How do I replace images with any other technique for better SEO?

Question: My website has many images which aren't good since we have a lot of content inside of them which Google won't know about. So by using CSS or JS isn't there a solution with which we can convert these into a better understandable format for Google?
Answer: All you really have to do is to make sure that all of the images that contain text that you want to be indexed have proper alt attribute with that text. This is important not only for Google but also for people with screen readers and text-mode browsers.
The best way to test your website is to see how it looks like in a text-mode browser like Lynx, Links or w3m. You can also try the Online Lynx Viewer and the Fetch as Google tool.
See also:

Search Engine Optimization Starter Guide by Google (download the PDF on that page)
Webmaster Guidelines: Best practices to help Google find, crawl, and index your site
Comment: Greetings, alt tags are there. but when we talk about ranking signals. alt tags hardly contribute 1% while content can be a very major part in this.
Answer: Instead of using images, try using text and CSS. You can do something like the following.
HTML:
Call us now to order!

CSS:
a.call-button {
  display: block;
  width: 100px;
  height: 100px;
  background-image:url('imageofphone.png');
}

So basically you create an image without any text of what you need. Then create an anchor the same size as the image and place it as a background within the element.
To Google, the link is just a clean text link as you can see from the HTML above, but to visitors they will see all the fancy images.
The only downside is that the text may look a little boring unless you use CSS on them.
Answer: If you are talking about complex images that contain lots of text/data (like scans of paper documents, pie charts, infographics etc.), one possible way would be to use the object element.
Example use for a scan of a written letter:
<object data="scan.png" type="image/png">

Hello John!

I'm sorry for not writing to you earlier, but I …

You can find the video at http://example.com/video, I hope you enjoy it.

…

Yours sincerely …

</object>

If the users client can/shall display images, scan.png should be shown. If the client is not capable of displaying images (text browsers), or the user has disabled images (low bandwidth, screen reader), or images can't be parsed (search engines), or the image resource doesn't exist (404, server down), then the fallback content should be displayed/used, which is the content of the object element.
For the fallback content, you can use HTML elements in the Flow content (including simply text) and Interactive content categories.
Note that browser support wasn't the best in the past, but I guess today most browsers should have no problems with object (probably see this question), especially not if used for images. Regarding SEO: I don't know which/whether search engines handle object fallback content correctly; can't find documentation or tests. In this question it says that the "Fetch as Google" tool didn't display the object element resp. the fallback content at all (don't know if it is or was true, though). Honestly, I can't imagine that Google would ignore the fallback of object elements, as this element is specified more than 14 years ago in HTML 4. Search engines that don't know/understand object would treat the fallback content as "real" content, because it is not "hidden" in an attributes value (like alt); for them, the fallback content is just normal HTML enclosed in an "unknown" element.


How do I add more training data to pre-trained deep learning net

Question: Am kind of new to deep learning. I have however trained a number of face images and achieved relatively good recognition rate. Now my question is if my client will be taking a few more pictures daily or weekly, how will that be integrated. Or will they have to train again, is there any fast way of adding training data to a pre-trained net?
Comment: Are the new faces from new classes? If so this is a transfer learning problem.
Answer: Although it depends on the library you use, in TensorFlow you can import weights for an existing model and continue training on new (or existing) data. TensorFlow calls this "checkpointing" and I believe it was primarily intended for cases where your model would take too long to train in a single session and you need to pause and resume training later. What you're trying to do is very similar; the only difference is that your data will contain a few more records than before. Reading your new/bigger data set is as simple as just pointing to a different CSV file.
Here is a good example on Stack Overflow of TensorFlow checkpointing: https://stackoverflow.com/questions/33759623/tensorflow-how-to-restore-a-previously-saved-model-python
Answer: Step 1: Save the weights
(New data comes in)
Step 2: Make a new dataset (E.g. add new data to the existing dataset or create a completely new)
Step 3: Initialize your model to weights you previously saved
Step 4: Proceed to train on the new dataset (Save the weights after)


Αre these three dots over a note supposed to be staccato?

Question: I'm learning Rhapsody in Blue. In the second and third measures(of the below portion) some of the chords have three dots over them. Are they staccatos? I am not sure how to play them. The only information I was able to find is that the notation is sometimes used in orchestral music.
Comment: The notation in the second bar, with one slash on the stem, a triplet and three dots is shorthand for exactly what is written in full in the first bar.
Comment: @LaurencePayne You should make your comment an answer.
Comment: possible duplicate of [Four dots over tremolo minim (half note with slash)](http://music.stackexchange.com/questions/7527/four-dots-over-tremolo-minim-half-note-with-slash)
Answer: As Laurence Payne's comment says, you've encountered one form of musical shorthand. There are a few layers of shorthand here so I'll break it down for you.
Stripping the first of the first measure of the second line of any shorthand markings, we have just a dotted eighth note.
Now we'll look at that slashy mark across the stem. It just means to subdivide sixteenth notes. A dotted eighth note can contain 3 sixteenth notes. So so far, we have just that: three sixteenth notes, represented by the dotted eighth with the slashed stem.
Secondly, we'll add the little 3 into consideration. Placed above our three sixteenth notes, this creates a sixteenth-note triplet. (Hopefully you are familiar with those.)
Lastly, those three dots above the eighth note indicate that the notes in our sixteenth-note triplet are staccato.
Like Laurence Payne said, it's really the exact same rhythm as the first measure of the first line, but hopefully this more detailed explanation helps you understand the notation a little bit better.
Comment: The three dots are not a "reminder" of anything. They are staccato dots over the three repeated 16th-notes.
Comment: @alephzero Ah thank you! I will edit my answer. I should have fact-checked rather than relying solely on how this stuff was explained to me.
Answer: It must be a shorthand way of writing what's in the previous bar: instead of writing all three triplets out, he's written one, with the '3' over it, saying it gets played thrice. As each chord needs to be staccato, he's put three dots over it, to signify each staccato.
Comment: @AsianSquirrel - when a note is subdivided by three, the three are triplets anyway, I think.
Comment: Ah is that what it is? The 3 simply indicates subdivision (like the slash), not triplets? (I guess I know a lot less than I thought I did.)


How does flicker relate to a card like Ulamog's dispoiler

Question: I was wondering how a card like Flicker and a card like Ulamog's Despoiler would work together. Since Ulamog's Despoiler returns a card from exile and flicker exiles a card snd then returns it would flicker return the card that was put into a graveyard to the battlefield or would it just stay in the graveyard? I tried to look at rule 400.7 but I got confused on if it would work. If anyone could help me I would be very grateful.
Comment: @Bootskat If you want to know about cards which have significantly different effects from Flicker, please ask that in an entirely new question not as comments to this question. Thanks!
Comment: They won't interact in any way.  You have to completely finish resolving Flicker then the Despoiler's trigger can resolve (or in the opposite order).  Basically you can't pick the two cards to move from exile to the graveyard while Flicker is resolving.  For Flicker, you move the card to exile then back to the battlefield before anything else can do anything.
Comment: What are you trying to flicker here?  Something other than the Despoiler?
Comment: Yes, I am trying to flicker a permanent a opponent controls
Comment: Ok, thank you, do you know how it would work with a card like Admonition Angel?
Answer: You can't cast or resolve anything whilst the target of Flicker is in exile, as it is returned to the battlefield as part of the spell.
You could do it to the target of Otherworldly Journey, as that returns the card at the next end step. If you did, it would stay in the graveyard, the object in the exile zone that Journey is looking for is no more.
Answer: Flicker and the Despoiler won't interact in the way you want them to.  You can't Flicker something to exile and then move it with the Despoiler while it is there.  The stack won't let you do that.
The stack defines the order things are done in.  You have to completely finish resolving one spell / ability before you can start resolving another or put something else on the stack.
So if you cast Flicker targetting an opponent's Hill Giant, the stack looks like this:

(top of stack)
Flicker
(bottom of stack)

If you start resolving Flicker without anyone responding, it will move the Hill Giant to exile then immediately back to the battlefield before you can do anything else.
If you were to cast Despoiler and respond with Flicker you still end up in the same situation.  The stack would look like this:

(top of stack)
Flicker
Despoiler
(bottom of stack)

You'd resolve Flicker (moving the Hill Giant to exile and immediately back to the battlefield).  Then you'd go to resolve the Despoiler.  At that point the Hill Giant wouldn't be in exile so you couldn't touch it with the Despoiler.
And just to be clear, you couldn't put them in the other order on the stack under normal circumstances (you can't cast a creature while the stack isn't empty).  Even if you could with some shenanigans, the Despoiler would resolve before Flicker while the Hill Giant is still on the battlefield.


Why is Mr. Robot so anti-Chinese and why is this so widely accepted?

Question: Throughout Mr. Robot, we've seen protagonist in all colors and ethnicities. But for east Asians there have only been nerds, narcissistic villains, mask welding terrorists and manipulators throughout its many seasons. Why has this been accepted in the USA where equality is preached and why major movie critics are dodging this topic?
Comment: I marginally touced on this on another answer (I'll provide a link), but I think it's because the Chinese Goverment is one of the leaders on cyber securaty technology and that (by US standards) have questionable motives on the World Stage, which can be seen at times a threat. https://movies.stackexchange.com/questions/81733/in-mr-robot-season-3-episode-2-what-does-china-wants-to-annex-congo-mean
Comment: The other side could also have to do with American paranoya going back to communism and the red scare--but I'm behind on the series, so I am shooting in the dark without context. The following is also an interesting book I have been meaning to read: https://www.amazon.com/Operation-Shakespeare-Story-Elite-International/dp/1451655169
Comment: Why is it accepted - why wouldn't it be? It's fiction after all. So many anti-Russia and anti-other-things have been made in the past...
Comment: да, действительно, фильм сводится к тому, что какой-то китайский пидор все натворил и подставил иран. и еще в фильме китайцы припудрены японской идеей камикадзе. мораль фильма вобщем-то "китайское правительство - пидарасы".
Comment: there are actually criminals and psychopaths of many ethnicities and races in  Mr.Robot - I don't think that your conclusions are correct.
Answer: I'm not convinced that White Rose's plan is entirely evil, so your premise may be flawed. (Well, clearly the means by which they go about it is evil, but the characters may feel it's justified to right what they perceive as wrongs.) We don't yet know enough about what the ultimate goal is to say one way or the other. She's talked about undoing all the bad things that E-corp has done, so it could end up being that she (or China in general) is the hero in the end. We don't really know how Elliot ended up working with them and arranging the whole plan or what the whole plan is.
The other thing is that the antagonist needs to be an entity that can plausibly do the hacking that needs done, and that also plausibly would have a reason. Since the action takes place in the US, that means finding an adversary to the US or at least a US-based corporation. Likely candidates are Iran, North Korea, Russia, and China. Iran and North Korea are the least plausible of that group, considering that the plot requires the US to concede to allow the antagonist to annex the Congo (or any other nation for that matter). They also need a way for characters from that place to be able to freely move about in the US without suspicion. That's probably difficult for someone high up in the Iranian government and impossible for a North Korean.
So that leaves Russia and China. Back before it was revealed in real life that Russia was attempting to directly manipulate the US elections, China probably seemed like a more probable candidate and the writers probably thought it would be an easier sell.
That said, you are right that they don't appear to show any East Asian characters in a positive light. It's unfortunate, and is probably for the same reasons that other shows do the same thing - partly ignorance, partly biases (conscious or not) on the parts of the writers and creators. This is an ongoing problem in Hollywood, though there does appear to be some movement towards fixing it. Recent shows like Crazy Ex-Girlfriend, for example, show a hunky Asian man as the romantic lead. And a few years ago John Cho played the male lead in the TV show Selfie. Maybe this is the start of something bigger? We can hope.
As for why no critics mention it? Well, some have, both positively and negatively. It just depends on where you look.
Comment: I havent set on this idea until recent episodes (s3ep6), at this stage i think white rose is clearly evil (and narcissistic obviously), s3ep5 white rose executed a plan that killed thousands. To be fair season 1 also shown Hispanic and Swedes, but Tyrell's character developed well and the dealer was bad ass intimidating. I don't think plant villains warrants the excessive amount of de-humanizing, there's been no drama scenes from East Asians at all while the show is saying "trust us, it is they who are the Ventriloquist".
Answer: My take on this has to do with real-life views.
First, I think that although there are lots of people in the United States who want equality, the reality is we are still fighting for it and arguing about what equality really is in a Democratic Republic and [some type of] Capitalist Nation.  So Mr. Robot may be reflecting a real-life bias.
Second -- As I mentioned on an answer of a similar Chinese-related question, there is also a real-world truth in that China (as in the Chinese Government) is seen as one of the strongest nations in terms of cyber technology. Mr. Robot is a show about how corperations due to both advances in technology and buying off Governments creating loopholes in laws, makes some Corperations as powerful, if not in some cases, more powerful than a nation. It's a show in part about about corporate globalizationism through greed and cycber espionage.
China is a player on the world stage that the United States has worried about for a long time--going back to Cold War mantality with the fear of communism and [the second] The Red Scare and McCarthyism. I once heard Hillary Clinton state a few years ago, but more so in regards to Russia, that she thinks the Cold War never really ended--and I think there is a fair arguement that that's true in the sense that Cold War just changed it's face with computer technology becoming the new technology that could make or break a nation, such as the Russian interference in Brexit or the 2016 US Presidential Election---but also when you look at a nation like North Korea, clearly the threat of a Nuclear War is still imminent.
The reason I brought up North Korea was because recantly on CNN when it was discovered (or revealed to the public) that North Korea was working on their own H-bomb (hundreds to thousands times the punch of WWII H-bombs), it was also revealed that China and Russia helped them with this bomb! Analyst have discussed some reasons why China has helped North Korea with backdoor things in past, being echonomically important to China, but I have yet here anyone really discuss why they would help with this specifically---and/or really get into "how" they helped (ie: resources, materials)--and if it was a faction of the Chinese Government or Chinese-owned/sponcered company/affiliate??? I think the media, probably due to national security reasons and, perhaps, not clear enough intellegence, is never really forthcoming when talking about other nation's endgames...
There is also this book I have wanted to read titled, Operation Shakespeare: The True Story of an Elite International Sting.

A secret war. A daring sting operation. The great untold national
  security story of our time: "An impressive and important work…The book
  has the glamour of a spy novel and the gravity of a meticulously
  researched exposé" (Christian Science Monitor).
On today's high-tech battlefields, the most lethal weapons are not the
  big ones, but rather the ones that are small enough to be smuggled
  inside a pack of chewing gum. Developed and manufactured in the United
  States at extraordinary cost, these tiny weapons of war—which can
  guide missiles, see through walls, and trigger anything from a
  wireless IED to a nuclear weapon—are what currently give the US its
  military advantage. Unfortunately, they are increasingly being
  discovered in the hands of our enemies.
In Operation Shakespeare, Pulitzer Prize finalist John Shiffman tells
  the true story of an elaborate sting operation launched by an elite
  Homeland Security team that was created to stop Iran, Russia, China,
  and North Korea from stealing US military technology. The sting,
  codenamed Operation Shakespeare, targets an Iranian arms broker who
  works on behalf of Tehran. Over the course of three years, the
  American agents go undercover to outwit not only the Iranian, but US
  defense contractors and bankers willing to put profit over national
  security. The chase moves around the world, and as the United States
  tries to bring the Iranian to justice, his own government plots to
  assassinate him, fearful of what he might reveal.
Tenacious, richly detailed, and boasting unprecedented access to both
  the Iranian broker and the US agents who caught him, "Operation
  Shakespeare reads like a spy thriller—but Shiffman's meticulous
  reporting leaves no doubt that he is telling nothing less than scary
  truth" (Daily News, New York).
  https://www.amazon.com/Operation-Shakespeare-Story-Elite-International/dp/1451655169

So although there might also be some more specific inverse reason why some of the Asian or Chinese characters are potrayed in a bias way, I'm a season behind so I don't have the context to give a stronger inverse answer, but it could be because they are cyber espionage Chinese agents, a rogue Chinese or Chinese-American(?) espionage company or crime syndacite, or it could just be a reflection about how the United States still worries about China and Chinese Interest-- and what their overall agenda is, which at times does seem like a threat to Democratic nations.
Answer: Your premise that it is "anti-Chinese" is flawed.
It is anti-China, which is very much different in a hard authoritarian regime where the government operates out of its own interest without regard to the self-determined interest of its people. That simple.
The series depicts very much the corruptible sides of the U.S. entity, as well. Grab a single point of weakness of the system, and you can get your interest through it by means of extortion. The show does not give much better credit to the U.S. government. Since the question, recently it has been revealed that China maintains informal global law enforcement primarily of its citizens and nationals, forcefully repatriating individuals abroad and engaging in transnational persecution.


Disable Hover effect for announcement webpart

Question: It may sound simple, but I`m not able to find anything relevant that can help to disable Hover Effect for Announcement Webpart Page. Looking for the CSS code that I can set on the Homepage and the Announcement page that Hover effect is disabled.
Answer: You will have to edit the list view that you are currently using for the announcement list. Edit the view and look for the option Tabular View and uncheck "Allow individual item checkboxes". No more hover effect.
Comment: My fault, change the view style to Basic Table, and you should be without the hovering effect. But still disable the tabular view to get rid of the selectable checkboxes
Comment: I`ve uncheck "Allow individual item checkboxes". However, hover effect still persist. Additional information, Style set to default. Any alternate option?


Call $created variable in content type node template

Question: How can I call the $created variable in my content type node template? I tried the following but it just produces what seems to be a random string of numbers:
        <?php print render($created); ?>

Answer: The $created variable is just a number, but it's not random it is a unix timestamp of the node created date.
Since it is not a render array you do not print it using the render() function, you would just print it like this:
<?php print $created; ?>

However that is also probably not what you want because you probably want a human readable date/time, not a unix time stamp.
As you can see in the main variable preprocess function for the node template (template_preprocess_node()), there is also a variable $date, which is a formatted date based on the $created variable.
That will default to using your website's medium date format.
You can use it like this:
<?php print $date; ?>

If that is not the format you want you can also manually use the format_date() function to format it to your requirements like this:
<?php print format_date($created, 'short'); ?>

or like this for something more custom:
<?php print format_date($created, 'custom', 'd/m/Y'); ?>

See the php date() documentation for more information on custom date format options.
Answer: This can vary from theme to theme so you can look in your template.php for the hook_preprocess_node(). This is where you can alter and set variables for your node.tpl.php. The $submitted variable could be used or modified in this case.
/**
 * Implements hook_preprocess_node().
 */
function my_theme_preprocess_node(&$variables) {
  // Alter the submitted variable, just on blog type.
  if ($variables['type'] == 'blog') {
    $variables['submitted'] = format_date($variables['created']);
  }
  // Or define a new variable for your node.tpl.php
  $variables['created_date'] = format_date($variables['created']);
}

Print the variable in your node.tpl.php
<?php print $created_date ?>


How read events from solidity

Question: I made a solidity contract but I want to get the event in another contract, is it possible to watch the event in that way?
Comment: I mean to watch an event in another contract
Comment: No. At the end of the function which emits the event, return the event values. Then, in any other function which calls this function, you can get these values.
Answer: No, events can be emitted by smart contract under Ethereum, but they are not readable by them. They are write-only.

How read events from solidity


Why does Googlebot keep coming back to recrawl pages that have been returning 410 for a long time?

Question: It was early 2018, almost two years ago, when I retired a bunch of pages from my site that were no longer needed/relevant/maintained/etc. I did that by returning a 410-Gone HTTP status. To my surprise, Googlebot still keeps coming back to those pages at very regular intervals, just to get 410s again and again and again. For 2 years. I have checked and those pages are not in the index anymore, but I'm curious as to why the crawler still thinks the page "might" be available? Does anyone know of a good blog/discussion that explains how 410s really work?
Comment: Would there be any internal or external pages still trying to link to them?
Answer: Once Googlebot finds a working URL, it will never forget it.  It will always come back to crawl it periodically.  It doesn't matter what status it returns.  It doesn't matter if it still has any links to it or not. I have URLs that have been 301 permanent redirecting for 15 years.  Googlebot still crawls them occasionally.
The logic appears to be that old URLs occasionally get resurrected.  Googlebot might as well check sometimes. The number of links into the URL determines how often it will get crawled.  If you manage to remove every internal and external link to the URL, it will get crawled far less frequently.
Googlebot even has a special crawl mode for old URLs with no links.   Sometimes I will find Googlebot requesting hundreds of such old URLs from my site over the course of a day.  When Googlebot is in this crawl mode, it appears to crawl the URLs in order of length.  The shortest URLs get crawled first.
This shouldn't be anything to worry about:

As long as the URL is returning a "410 Gone" status and you allow it to be crawled, there is no danger that Google will index the URL.  Googlebot is simply checking to make sure the page is indeed still gone.
404 and 410 status URLS don't usually consume many server resources.  They are very small responses.  They don't usually require database lookups.  They don't usually trigger additional resource requests for JS, CSS, and images.
Google expects to find 404 and 410 errors on properly configured websites.  Serving these error pages to Googlebot won't hurt the rest of your site in any way.  It doesn't matter if there are 100 or 10 million error URLs according to Google's John Mueller
Answer: Regarding a good blog/discussion, there is one here
https://www.searchenginejournal.com/google-404-status/254429/

"If a 404 error goes to a page that doesn't exist, should I make them
  a 410?"
John Mueller answered:
"From our point of view, in the mid term/long term, a 404 is the same
  as a 410 for us. So in both of these cases, we drop those URLs from
  our index.
We generally reduce crawling a little bit of those URLs so that we
  don't spend too much time crawling things that we know don't exist.
The subtle difference here is that a 410 will sometimes fall out a
  little bit faster than a 404. But usually, we're talking on the order
  of a couple days or so.
So if you're just removing content naturally, then that's perfectly
  fine to use either one. If you've already removed this content long
  ago, then it's already not indexed so it doesn't matter for us if you
  use a 404 or 410."

And from the article link official specs for 410 error code
https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.11


What is the format for logging into a domain account in OS X?

Question: At the login screen, how do I login to a domain account?
For example, on Windows the username might be something like email@example.com, where the domain is contoso.local.
Edit: The AD username happens to be the same as a local username.
Answer: You need to set up Network Account Server settings in Preferences > Users & Groups > Login Options.
In the company I work for I can either use DOMAIN\username or username@DOMAIN when logging in to the AD on from a Windows Machine, but on the Mac this is not required. I just type in username and my AD password, and it logs me in.
Comment: What if the AD username is the same as a local username?
Answer: I've been having the same issue today and I believe I've resolved this (Yosemite).
I've got my local user (user.name) and my domain user (domain.local\user.name). I've added to OD auth correctly without issue.
When I attempt to log in with my domain user (domain.local\user.name) it rejects me for an invalid password. I tried out the password for my local user, and it worked, but threw an error when loading the desktop.
I've right clicked on the user under "Users & Groups" and gone into "Advanced Options" (which I found completely by accident). I then modified my "Full Name" - which was user.name - to be user.name.local.
After rebooting the machine, all worked and I could log into the domain user with the correct password without issue.
One thing to note here is that I didn't have to change the "Username" in advanced options here. There may be ramifications to this - see this Apple support KB for more information.
Answer: You can control this by setting the search order for each domain in the forest. This can by found on the Mac by going to:
System Prefs->Users & Groups->Login Options->Click Edit next to Network Account Server
Then
Open Directory Utility and Click on Search Policy
Answer: mwidman has given you the answer for this.
If you wish to log in to your Active Directory domain account rather than the local account then precede the account name with the AD domain name and a .
So in your case contoso.local\louis
This assumes that you have already bound the Mac to Active Directory. I am also wary of using Spider-moe's solution - as a sysadmin I never like altering the search policy order.


upsampling in the frequency domain

Question: I have the Fourier transform $S(\nu)$. If I oversample by a factor $R$ in the frequency domain. Does the duration of the signal $s(t)=IFFT(S(\nu))$ change?
Comment: You seem to be mixing continuous-time and discrete-time concepts here. Could you try to clarify what you mean? At the same time, review the concept of "duration" of a discrete-time signal.
Answer: If by "oversampling", you mean interpolating more frequency samples between your existing frequency samples, then in this case this would have the effect of zero padding your time domain waveform. Therefore the duration of your signal itself doesn't change, but the duration of time over which the DFT is performed would, with the addition of zero padding to fill out the added time duration (which could be before or after the waveform, changing the phase component of the resulting frequency spectrum accordingly).
To understand zero padding it is helpful to understand the difference between the Discrete Fourier Transform (DFT) and the Discrete Time Fourier Transform (DTFT). The Fast Fourier Transform (FFT) is an efficient algorithm for computing the DFT.
Zero padding a discrete waveform in time results in interpolation of DFT result in frequency. The DFT result is discrete, given by samples of the DTFT. The DTFT in contrast is a continuous function in frequency. By zero padding, we introduce more samples on this same DTFT.
Comparing the formulas for the DFT and DTFT will give you further insight into why this is so:

Here the plots show how the DFT is samples of the DTFT, and by adding zeros to the time-domain waveform prior to taking the DFT (zero-padding), we are approximating the continuous DTFT by filling in more samples (interpolation)-- the more zeros we add the closer we can get to the continuous waveform DTFT. So zero padding and interpolating the frequency spectrum are Fourier Transform pairs.
Further notes:  In the plots I say that the DFT is repeating in time, but in actuality it is only given over N samples. The repetition in time is a mathematical equivalence: similar to the Fourier Series Expansion which is defined over a finite time T, it's frequency components only exist at integer multiples of 1/T (discrete in frequency). If you allowed the time domain waveforms of those components to extend to $\pm \infty$, the base waveform that was defined over t=0 to T would repeat in time. The DFT as given above would be the same as the DFT of the same waveform repeating in time, and seeing that helps provide a lot of insight--- anything that repeats in time MUST be discrete in frequency, anything that is discrete in time MUST repeat in frequency (A/D sampling is an example). The DFT does both. Since the DTFT is performed on a single time domain waveform over all time, it never repeats in time and for this reason has a continuous frequency response.
Answer: Oversampling a spectrum is a non-linear process. Specifically, since each bin is suppose to represent an integral number waves in the sampling window, oversampling must be done in accordance with that. But to answer your question, and assuming the spectrum is of some finite time domain window, the new time domain window duration is the wavelength of the lowest frequency bin in the FFT.

upsampling in the frequency domain


How does a keyboardist (as the lead singer) display good, energetic stage presence?

Question: I play the keyboard in a band and am also the lead singer. How can I have energy and good stage presence while focusing on my playing and being confined to a several foot area of the stage?
Comment: Watch some Elton John live videos, especially from his younger days.
Comment: Leon Russell, Billy Preston, Jerry Lee Lewis, and more. The one thing they all project is their attitude. It's very obvious who's the boss on their stage. There's no shyness there.
Comment: Adding to skinny peacock's answer, the musicians listed above all tend to have the piano sideways at the front of the stage, so they are free to move and are accessible to interact with the audience, rather than being trapped behind a keyboard.
Answer: Firstly, get so you don't have to focus on your playing. Get so you know the set pieces. Either verbatim or to be able to carry on when you fall off the stool, and pick up from anywhere. You may need to be able to play exactly the same things each time, or happier being able to change harmonies, sounds around to suit the mood at that moment. Either way, the playing needs to be flawless in its execution.
Then you can start to think about the other aspects of leading.
Place yourself in a prominent position. The audience needs to see you, but so does the rest of the band, for cues. What, there aren't any, or need for them? Make a need. Bring the guitarist in to his solo, swing round to the drummer for his break. Even be histrionic!
Watch other piano players such as Billy Joel and the aforementioned Elton John. Even Stevie Wonder produces 'stage presence'!
Ring the changes by sometimes standing, sometimes sitting. Get clever and play the piano from the back of it. Yes, just for fun. You need to be fit to do all this, so keep yourself fit. Can't sing well out of breath...
Also, consider that some numbers can be performed without keys. Get away from the 'boards, grab a mic, and be the frontman!
Answer: You don't need gimmicks.  Look at the audience, sing TO the audience.  You can do that standing or sitting, behind a keyboard or holding a guitar.  You've already been given a list of role models!
Answer: If you are the keyboardist, then unless you have a keytar, you'll always be confined to that area in which your keyboard stands.
Most audience members will notice how you look first before how you sound.  And usually the keyboardist looks the most boring compared to everyone else.  The ones with good stage presence would do some variation of the following:

Use upper body and move to the music (unless of course you are singing at that moment).
Don't look like you are bored (I've played with too many keyboardists who look bored as hell and it's distracting to the audience - they could care less how well they play).
Head bob when appropriate.
Use simple dance steps if you are playing some easy chord progression.
And smile once in awhile.

Some people might laugh at this.  But you'd be surprised how many "professional" players don't do this.  And the audience isn't stupid, and don't treat them like they are because they don't know you hip chord progressions. They are the ones paying your wage and giving you the opportunity to play.  Don't condescend to them.  If you aren't entertaining to them, then maybe you should consider doing something else, or be a you-tuber or session player.
Comment: "And the audience isn't stupid, and don't treat them like they are because they don't know you hip chord progressions." -- Well, they don't even know the _un_-hip chord progressions. In any case, it is unclear at whom this final section of the answer is directed; certainly not at OP; the whole point of the question is to obtain practical advice about improving stage presence.
Comment: @DavidBowling This answer was about improving stage presence, as the OP had asked.  It may come off as laughable, but you'd be surprised what people respond to.  "Well, they don't even know the un-hip chord progressions." -- Exactly, my point is that your stage presence is what people see, not hear.


If signature based AV software is becoming obsolete, what is the home user to do?

Question: Assuming one is a worried home user who keeps certain sensitive files, works on personal projects, and generally wants to ensure the integrity of their single system (to keep it simple), what's a user to do? Signature based AV software is being spoken of as quickly becoming obsolete, where does this leave the average, or even power home-user?
Comment: @techraf I think OP is concerened that the very concept of singature based AV is becomming obsolete, not that his particular definitions are getting old. So automatic updates is not the solution.
Comment: @techraf, Anders has hit the question bang on. I say "quickly" mainly due to my limited knowledge of the AV field, and I do not want to make blanket statements, per se.
Comment: Use a firewall. Most viruses are moot if they cannot communicate with its command host.
Comment: @Empathy : What if it uses standard HTTP just like my web-browser? What if it is a malicious add-on or plugin in my browser?
Comment: @Matthew1471 the application would need to granted outbound access, just like the browser. Good point on the browser plugins, as this is nowadays the most common method of infection. Chrome seems to be a very secure browser however.
Answer: Since you can never be 100% sure you haven't been compromised, you need to practice defense-in-depth and just aim for as close to 100% as is practical.

AV software is becoming obsolete, but it isn't there yet.  Keep it around, keep it updated, and run it often.
You already know which files are your most sensitive.  Back them up often, and keep a copy off-site, so that if they are lost (i.e. from having to wipe your system), you can get them back.
If you're flexible about the single-system thing, have a machine that never connects directly to the internet.  Carefully mediate what files move across from your offline machine to the one you use to browse.  You can't call it an air-gap, but it's close.
Disposable virtual machines are your friend.

Defense-in-depth means that if one of your countermeasures fails, another will step in to stop the threat.  The more you have, and the more they compliment each other, the safer you'll be.  Just not 100% safe.
Comment: #2: backing up sensitive files doesn't address confidentiality. You should encrypt your sensitive files and backup off-site. In this way, if the hacker gets into your machine, he won't be able to read the content of your sensitive files, at least not in a reasonable amount of time.
Answer: A lot of AV software has switched to also include heuristic based detection. While a particular piece of malware might not be known to the AV company or match their signatures, the fact it opens up a socket to a mail server, sends lots of traffic, registers on start-up of my computer and is a hidden program with no window might for example be flagged as "suspicious" and cause an alert.
See Heuristic analysis.
My favourite impartial AV testing site AV-Comparatives perform a number of tests against products, one of which is to use out of date virus definition files and then give them viruses that are now known and see whether the AV product would have heuristically decided it was a virus without any prior knowledge of it (AV-Comparatives Retrospective Test).
Comment: Interesting website. Are they still functional? I ask because there seem to be gaps in the data. Nonetheless, it's great to see this sort of analysis being done. Thank you.
Comment: Hi Hammy, Glad you like it, I'm constantly surprised how niche that site appears to be online too. They appear to have done a recent "Real-world" test : http://www.av-comparatives.org/dynamic-tests/ so certainly still seem around but maybe there's less demand to test the specific individual detection components of AV, so they're focusing more on what users ultimately ask ("What AV product will catch the most?"). I'll tweet them :-).


What is this movie with creature scared off by bright light?

Question: In this suspense/thriller movie which was probably early 2000s,  a blondish young woman sees a spiderlike creature crawling on the ceiling. She is later put in a mental institution, but later she is discharged because she lied that she no longer sees the creature. The movie ends with the woman alone in her bedroom, surrounded by high powered lights and lamps.
Comment: Can you remember when you watched this? How long ago it was? What the creature looked like? How come no one else saw it? If you have anything else to add you can [edit] your question to add it.
Comment: You could improve this question by going through the checklists [here](https://scifi.meta.stackexchange.com/questions/9335/how-to-ask-a-good-story-id-question) and editing in any relevant info you can think to add.
Comment: Possibly Boogeyman - or one of the two sequels. I've only ever seen the first hour of the initial film, there was a girl who was convinced she had a Boogeyman hidden in her ceiling. Near the start the male protagonist (who had witnessed a Boogeyman attack) slept surrounded by bright lights so it's likely the girl decided to do the same. The film was too dull to watch until the end so I don't know
Comment: I can't remember when the movie was..probably around early 2000s. The creature wasn't clearly shown.I seem to recall it resembling a crawling spider.
Comment: It doesn't seem to be the boogeyman movie..The film was more on suspense, rather than horror. All i can clearly remember was the ending part with the bright lamps turned on.
Comment: possibly the same as https://scifi.stackexchange.com/questions/155274/movie-in-which-aliens-monster-cause-power-outage-and-kidnap-people-into-dark-dim
Answer: I haven't seen the movie myself, but with some help from Google, what you are describing sounds a lot like the alternative ending to the movie They
The movie starred Lauren Rogan, who is blonde.

Alternate endings
Two alternate endings were shot but neither of them
made it to the final cut, they include:

After the incident in the subway the film's plot cuts to nine months
later where Julia is shown hospitalized in a mental institution. Julia
manages to convince a panel of psychiatrists including Dr. Booth that
she has regained her sanity. She then sees one of the creatures climb
through an air shaft in the ceiling but continues to deny their
existence. She is finally released and proceeds to set up high powered
lights all over her apartment room. The camera then pulls out of her
bedroom as she is seen sitting on her bed. A door creaks open in her
darkened hall and the film cuts to black. (This ending was shown to
test audiences which was deleted and re-filmed after test audiences
responded negatively to the ending, for some reason this ending is
unavailable in any DVD.)
Julia wakes up in the mental hospital and
sees that all the people in her story − Dr. Booth, Sam, Billy, Terry -
are patients in the mental hospital and her boyfriend Paul is a doctor
working there. The doors to Julia's room then break open and one of
"them" enters and seemingly attacks her until it is realized that it
was all a delusion fabricated by Julia's mind and she had been
suffering from Schizophrenia throughout the whole movie. (Some
versions of the DVD and all Blu-ray versions have this ending
available.)

And from IMDB, the alternative ending you remember was described as part of the work print:

The work print features this alternate ending which is not available on DVD anywhere. When Julia is knocked out in the subway it cuts to 9 months later in a mental hospital. Julia convinces a panel of psychiatrists, including Dr. Booth, that she is cured. She sees one of the monsters climb through an air shaft in the ceiling, but continues to claim that "They" don't exist. She is released and goes home only to set up high-powered lights all over her apartment. The camera pulls out of her bedroom as she sits on her bed. A door creaks open in her darkened hall and it cuts to black.

So it sounds like you saw the movie before it was released.  And the ending you are remembering can't be found on any DVD's
Comment: Wow that's it. Thanks so much. At first, I really thought it was They 2002 film but when I watched searched it on google and even watched it online, the scenes I remember aren't there and the ending is "wrong". I searched alot about alternative endings to They, I only found the Japan version which she didn't get captured at the end but just got institutionalized.


Why there can be different parametrizations?

Question: I've been getting started with fiber bundles and I'm really confused up to now. The definition I have is clumsy and incorporates three things: local trivializations, transition maps and structure groups. It is in short like that:

A fiber bundle is a tuple $\xi=(E,B,\pi,F,G)$ where $E,B,F$ are topological spaces respectively called the total space, base space and typical fiber, $\pi : E\to B$ is a continuous surjection such that for each $x\in B$, $\pi^{-1}(x) =F_x$ is a space homeomorphic to $F$ called the fiber at $x$ and $G$ is a topological group of homeomorphisms of $F$. Those items should satisfy:

There is an open cover $\{U_i\}$ of $B$ such that for each $U_i$ there's $\phi_i : \pi^{-1}(U_i)\to U_i\times F$ homeomorphism with $\pi_1\cdot \phi_i = \pi$ where $\pi_1$ is the projection onto the first factor. From this follows that $\pi_2 \cdot \phi_i = \tilde{\phi}_i$ is a homeomorphism between $F_x$ and $F$.

Whenever $x \in U_i$ we can consider the restriction of $\tilde{\phi}_i$ to $F_x$, the map $\tilde{\phi}_{i, x}$. Given $x\in U_i\cap U_j$ we can form the composition $\tilde{\phi}_{i, x}\circ \tilde{\phi}^{-1}_{j, x}:F\to F$ which is an element of $G$ for all $x\in U_i\cap U_j$ and $i,j$.

The induced mappings $g_{jk} : U_j\cap U_k \to G$ by $g_{jk}(x) = \tilde{\phi}_{j, x}\circ \tilde{\phi}^{-1}_{i, x}$ are continuous. They are called transition functions and satisfy $g_{jk}g_{ki}=g_{ji}$.

Now, condition one is clear, it says that locally the bundle is a product. Condition $2$ is complicated for me. The reason: I don't understand why there are many parametrizations and why their relation is important. The book says that the transition functions are the all important thing that gives the structure of the bundle, like the twisting of Möebius' band, but I can't see how.
I found an article on that example that said the following:

Say we want to parameterize the Möebius' band by a point $\theta$ on the circle, and a real number $f$ in the interval $(0,1)$. Concretely, say $\theta= 0$ and $f =\dfrac{3}{4}$.  Now, we transport the point around the Möebius' band by increasing $\theta$ and keeping f fixed at $\dfrac{3}{4}$. When $\theta\to 2π$, we should return to the same point $q$ in $E$, since it corresponds to the same $\theta$ and $f$, and hence the
same $q$.  However, because of the inescapable twist in the band, the point we return to is associated with $\theta= 0$, $f = \dfrac{1}{4}$.  Our parameterization for $F$ somehow "flips" when we move one turn around the Möebius' band.

Now, I really can't understand it. How can those functions give two differents parametrizations? I can't get this intuition, on how those functions somehow give us the twist in the band.
How all of that works? Is there any other way to understand this?
Answer: Cut the Möbius strip into three parts. Each part has a trivial fibration. Mark an up direction on the fibers of each part. This is completely at will, there is no natural preference of direction. The glueing together to form the Möbius strip can then proceed on the first two overlaps as up-to-up, but on the last it is up-to-down. As group elements of $G=\{-1,1\}$ this is just $(1,1,-1)$. Again, the position of the $-1$ is completely random, and also a glueing together with $(-1,-1,-1)$ is possible.


Sorting Data in Excel

Question: I have recently been working on a data table in Excel containing measurements of fossil specimens. In addition to containing things like the specimen number, species name, etc., the table also contains measurements from the fossils in question. However, because several specimens have data from both the left and right sides of the specimen, I often end up with situations where a single entry spans multiple rows, which means I cannot sort the data.
I have looked elsewhere on the Internet for a solution, and the only response I have gotten is that Excel doesn't really work well with entries spanning multiple rows, and I should reorganize my data. I understand that, and I have been looking for an alternate way of organizing the data. However, I have not been able to find an easy way to organize the data. I have tried reorganizing the information so each entry spans multiple rows, but when I do this it becomes very easy to make mistakes and to lose track of the data. It also becomes difficult to compare the data, since the measurements on the left and right side of the specimen are essentially the same thing and I cannot easily compare them if one specimen has a bone only preserved on the right side and the other specimen has the same bone preserved but only on the left side.
I have also tried organizing the measurements into a separate sheet which could be accessed by a hyperlink from the main sheet, but this has also posed problems. Because in this case the measurement data still cannot be sorted by specimen number of species name, if a specimen number or species name changes (which it has in the past), I have to manually reorganize all the hyperlinks by hand.
Finally, I have also tried adding an identifier to the multi-row entries, but this has a tendency to get screwed up if I sort the data, and it also mixes up any equations I use in the sheet. I might be doing it wrong somehow.
The good news is I am not interested in sorting the specimens by measurements, so if there is any way to organize the table so it is sortable but the measurements cannot be sorted, that is fine. At the same time, because all specimens technically have a left and right side (plus the average measurement between them), I could also work with a system wherein each "entry" spanned a set number of rows or subrows.
I was also wondering if it would be possible to write a macro to sort the data (especially since I am just sorting by the first five columns or so), or else do the database in some other program like Microsoft Access.  Any help would be greatly appreciated.
Answer: Everything you describe really breaks down to: "Excel is great for analysis; but I really should have stored my source data in a database." Accountants I have worked with almost always come to this conclusion eventually, once their data and reporting needs get sufficiently complex.
I suggest you invest the moderate effort to upload your data to a proper database, and learn how to download I as appropriate to Excel for specific analyses. The time effort will be well spent, and simpler by far than coercing EXCEL into tasks for which it is ill-suited.
MS-Access, MySql, and SQL-Server Express are all suitable for this type of upgrade. MS-Access, if already available in your Office subscription, has the advantage of integrating even more easily with Excel than the other two, and also uses VBA as it's macro language. The other two offer more complete and powerful implementations of the SQL language. All told, use the one most easily available to you.

Sorting Data in Excel


What do Tech Points do in Chrono Trigger?

Question: I have been playing Chrono Trigger and I noticed that at the end of most or all battles, I get "Tech Points" along with experience, money, and items. I have not yet seen what effect these Tech Points have. So, what do they do?
Answer: "Tech Points" are similar to experience, but they help to unlock more of the techs (and/or spells) each character has access to.  Unlike in other games, you don't learn techs based on your level.
In the "Tech" menu, you'll see a list of the techs each character can learn, and you can see how many more TP it will take to learn the next one on the list.  Confusingly, these are referred to as "Skill Points" in the tech menu.
Comment: OK, I get it now. I didn't realize that's what it was because the tech menu I'm looking at displays it as Skill Points needed instead of Tech Points.
Comment: @murgatroid99, yeah, it's been a long time, so I'd forgotten this, I was just editing it in as you posted this comment :P


Is it better to use the original battery for my d7200 camera or choose an third party replacement is OK?

Question: I got the original nikon d7200 batteries before, but its first initial 1st charge drains very fast. I tried to used them for a couple of weeks so they have definitely run down. And up. They've gone from full to empty very fast.
Does anyone have any experience of using third party batteries like LP Neweer Vemico or some other brands?
Comment: Don' t be too cheap. The most expensive "generic" batteries still costs one-third of the brand ones and work well (I'm using only these (BaxxtarPro, FWIW) on my camera now, my Canon battery being pronounced dead). The really cheap ones may have cut some corners to reduce costs....
Answer: I have no experience with either of those brands, but I do have some experience with third party batteries (for Canon).
In general the ones I have tried are just as good as the original. In the beginning.
Over time they tend to lose max capacity faster than original batteries.
Considering that they only cost half-ish of what an original battery costs, this is still okay, as they still have a lifetime that is more than half the lifeime of the original.
But.. I must also add that I once had a third party battery that started making a weird sine-sound that were getting louder and louder while charging. Fearing it might explode, I took it out of the charger, and the sound slowly died away. After that I threw the battery away.
This has happened once in approx. 8 third party batteries and never with an original.
The point is that while third party batteries ARE cheaper and provides an okay alternative, they might not have underwent the same quality control as the originals,
Answer: Camera maker batteries will usually be of more consistent quality.  Third-party batteries tend to be more variable.  Even the same brand could have different underlying OEM or design over time.  People also have different standards for good-enough performance.  For every success story, there are corresponding horror stories, using the same batteries.
If you have low tolerance for surprises, use the camera manufacturer batteries.  If you like to experiment, feel free to try third-party batteries from different makers until you find some you like.
Answer: The original battery is best in terms of being sure it is suitable for your Nikon D7200.
With that said, I find that Patona batteries are just as good.
Ravpower batteries also have a good reputation.
Comment: What does "best" mean to you? Best value for your money? Or best choice if some sugar daddy offered you whatever battery you wanted for free? If you offered me a choice between Battery A that can be charged a thousand times, and costs me $50, or battery B that will only last 500 cycles, but only costs me $12 and nobody who's purchased one from Amazon has complained (so far) about it catching fire in their camera bag; then I'm probably going to go with choice B.
Comment: Best as in being sure that the batteries are suitable for the Nikon D7200 from the point of view of safety and charge.

Some third party batteries are rubbish and best avoided.

That is why I recommend Patona from personal experience for Nikon to save others time in terms of research.

I've also found that Ravpower are very good for Sony alpha cameras.
Answer: Google found this on ApoTelyt, which I thought summed it up quite nicely

What about generic battery packs?
Nikon sells the original EN-EL15 pack at quite a steep price. This
premium pricing strategy has left room in the market for third party
suppliers to offer fully compatible battery packs at much lower
prices. Savings from buying generic replacement batteries can amount
up to 70 percent of the price of the genuine battery pack.
Indeed, one can easily find a variety of competitively-priced EN-EL15
replacements from different vendors at major online platforms (see,
for example, here on eBay). All these generic alternatives should work
fine with your Nikon D7200. So why would anybody then buy the more
expensive original battery?
Well, below are some arguments in favor of the genuine EN-EL15, which
can perhaps be summarized as "peace of mind".

Assurance that the warranty of the camera will not be rendered void if a battery-related failure occurs;
Assurance that the battery pack will indeed have the stated capacity;
Assurance that the battery will have low self-discharge rates and, thus, will hold its charge even when not in use;
Assurance that the power unit will not trigger any warning messages on the camera and can be effectively charged with the standard
charger;
Assurance that the manufacturing process has respected the safety guidelines for Lithium-Ion batteries;

That said, I'd tend to also trust makes I've already heard of - names you find in every supermarket, such as Energizer or Duracell.
Answer: You can find numerous teardown and analysis videos/articles on third party batteries and chargers on the net.
Modern camera batteries have internal circuitry, responsible for working "with" the charger and camera to make sure battery lifetime is optimized by ensuring correct charging and discharging, and for compensating for environmental temperature, and for ensuring that any battery or charger failure will never be catastrophic. The circuitry found in many third party batteries appears to be substandard in many cases.
Quality on third party batteries is found to not necessarily correspond to price - some branded third party ones are cheaper unbranded grades relabelled.
The same applies to charger circuitry design. Mixing random third party chargers (probably especially those that did not come with the third party batteries) with random third party batteries is likely the worst combination - you might have a situation where the battery designer assumed they could cut corners since the charger will take care of things, and the charger designer assumed the battery circuit will...
Consider secondhand but good camera batteries - in my experience, they can still be better  than some of the third party ones.
Answer: Rechargeable lithium batteries can be surprising complicated. In general there is "Protected" and "Unprotected". The difference is whether the battery has a builtin circuit board to regulate/protect the charge/discharge rates. For cameras you should be dealing with protected batteries. Unprotected is generally relegated to high power high current devices.
The D7200 uses the EL15 battery which comes in 4 variants. The differences are manufacturing date and embedded printed circuit board (PCB). I believe the D7200 can use any of the variants.
All of the Nikon branded batteries are rated as 1900mAh. Nikon does not manufacture the batteries directly, they brand them from vetted battery producers. That said, there are other unbranded batteries produced from the same manufacturers and of the same quality and specifications for less cost.
While there are excellent non-Nikon branded batteries, the catch is which ones? If you want to avoid the quandary, bite the bullet and pay the Nikon premium for a known product.
If you want to go with an alternate supplier, here are a few suggestions:
1. Check the mAh rating.
If it's substantially less than 1900mAh or if it doesn't state it's energy capacity, I'd suggest avoiding it.
Some of the newer batteries offer even higher energy capacities of 2100 or 2200 mAh. This provides a greater shooting time, but it's not a huge difference, 10-15 percent at most. The larger capacity may throw off the battery level indicator a little bit as well but the difference should be trivial.
2. Verify the charger.
Make sure it will charge in your current charger or that you are getting a new compatible charger.
3. Check reviews.
As with any product, check the reviews.


Motivation for gradient descent method over canonical method (for OLS/MLE) for simple linear regression?

Question: I am beginner in machine learning and I am currently trying to find the motivation for gradient descent method.
I am confused why we want to employ gradient descent method for linear regression? I see the cost function the same as the OLS function, and gradient descent method here actually takes more effort than simply getting the derivatives equal zero.
Then why we always try to use gradient descent here? I am when the model gets more complicated , and also when we make more assumptions on the prior distribution of the theta(parameters). The optimization problem will become much more complicated.
Then will gradient descent method still survive in terms of this? And OLS/MLE method will not be able to predict the parameters?
I see OLS as minimize the cost, and the MLE method as maximize the prob, which is in essence the same.(reference http://www.cs.ubc.ca/~nando/540-2013/lectures/l3.pdf) Should I think gradient descent method as a improvement from the OLS method, while the E-M method(maximize the expected likelihood) as a imporvement from the MLE method.
Thanks in advance!
Comment: That's like asking "motivation for driving to get to the cinema over being at the cinema". You're confusing the journey with the destination. OLS is a destination. MLE is a destination. Gradient descent is one way to get to a destination.
Comment: @Glen_b Thanks!I will edit the problem, I mistook the lagrange method with OLS.You are right, I confused the journey with destination. Just to make sure, so OLS means minimize the cost, and MLE means maximize the likelihood? Does OLS and MLE always the same for any models? So that means it is the same destination(estimate the parameters), but different direction(OLS and MLE)
Comment: OLS does *not* mean 'minimize the cost' unless the cost is given by the sums of squared residuals.
Comment: OLS is only the same as MLE at the normal (assuming constant variance). OLS is MLE for the normal, but not for anything else. When you have y|x being normally distributed OLS and ML are the same destination, but otherwise they're different destinations. However, OLS is often useful even when it isn't ML (it's still BLUE, under the required conditions).
Answer: For ordinary linear regression, maximum likelihood and  least squares are the same, i.e., give the same answer (the maximum likelihood solution is the least squares solution, if you derive the so called ``normal equations'' you'll see this, also see the book The Elements of Statistical Learning which discusses this).
But this is separate from how you find that solution. Gradient descent is only one method to find the solution, and it's actually quite a bad one at that (slow to converge). For example, Newton's method is much better for OLS (using various numerical algorithms to avoid inverting the Hessian directly).
But you are right in the sense that for very big problems, gradient descent becomes more useful because 2nd order methods like Newton's method can be computationally very expensive (again, there are approximations to that too).
I don't think EM is relevant for OLS, it can be useful for optimizing non-convex problems (OLS is convex).
Comment: Thanks for your reply!So gradient descent is just a method to find solution for OLS? Also I still have a problem. Is MLE and OLS always the same? I can understand they are the same for ordinary linear regression, but as for more complicated problems like neural network?GMM?LDA?..also I am wondering for the bayesian inference, MLE can somehow evolve to E-M, but does OLS still work? Many thank:D
Comment: Ah I do not whether it is still called OLS when the model is not ordinary linear regression, or maybe I shall say: does minimize cost and maximize likelihood always the same for all the models? so that means we can say we have two direction to solve the parameters estimation problem?
Comment: Not the same for all models: each model has its own loss function to be minimized (equivalent to the negative log likelihood for probabilistic models). Least squares is just the solution to one of these models (the Gaussian likelihood with known variance), it doesn't apply to all of them, for example, least squares does not minimize the logistic regression (binomial) negative log likelihood, so it's not useful there (although least squares is useful in practice here but that's beyond the scope of this comment).
Comment: Thanks for the reply! I misunderstood OLS previously. But I still have a problem :does minimize cost(different model has different cost functions) and maximize likelihood always the same for all the models?
Comment: Not all models have a likelihood. A support vector machine is not a probabilistic model, does not have a likelihood but has a cost function (=hinge loss). Example of models that do have likelihoods are linear regression, logistic regression, Poisson regression, Cox regression, etc.
Comment: Thanks for the reply!Ah I think probabilistic models also have a likelihood. Like we can estimate the parameters using MLE method.http://www.cs.ubc.ca/~nando/540-2013/lectures/l3.pdf


Can I compile Qt applications statically for rented software

Question: In cases where my software is only ever rented with a dedicated PC, is it permissable to compile Qt statically, as I would still technically own the program and it`s not being sold? Seems to be a bit of a grey area.
Comment: Could you explain how you are renting the software? Are you renting your PC to someone, and that PC happens to contain some (L)GPL licensed software? Or are you renting a physical medium that contains software, and letting someone use that for some period of time?
Comment: I will be renting a PC which comes with the proprietary software. They are renting both the computer and the software for a period of time.
Answer: The right to lend or rent a work out is, at least in the EU, covered by copyright law. This means that if you rent out a work that is covered by copyrights without permission from the copyright holders, then you are liable for a copyright infringement.
This ties back to the following definitions in the GPL license

To "propagate" a work means to do anything with it that, without permission, would make you directly or secondarily liable for infringement under applicable copyright law, except executing it on a computer or modifying a private copy. Propagation includes copying, distribution (with or without modification), making available to the public, and in some countries other activities as well.
To "convey" a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.

As the renters of your PC receive a copy of the Qt software, the conditions that the (L)GPL license places on conveying a copy must be met, which means they must be told about their rights under the license and given the possibility to exercise those rights.
The fact that they receive their copy on a medium that does not become their property is also catered for in the GPL license:

If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information.

By renting out the PC, you are giving the renters a temporary right to have the PC in their possession and to use it.
Comment: How about disabling access to the software's folder so the DLL' can't be replaced with other versions of Qt, etc?
Comment: @19172281: No, the end-user must have the right and possibility to run the application with Qt libraries of their own choice. You are not required to offer warranty and support if they do, but you are not allowed to use measures that make it extra difficult.
Answer: You are still subject to (L)GPL compliance. You always retain ownership over your software, and also have to comply if you issue a gratis license to your software. So that doesn't help you determine what your obligations are.
Instead, the L/GPLv3 defines:

To "convey" a work means any kind of propagation that enables other parties to make or receive copies.

Additionally, your device may count as a "User Product" in the sense of the GPL.
Renting your computers with the installed software is clearly a kind of conveying the software because the recipient could make copies of the software. They are not allowed to actually make these copies because it's your proprietary software, but you still need to respect the LGPL license.
The spirit of the LGPL license is that end users can modify the LGPL-covered parts. This is typically done by dynamically linking the LGPL components and providing the necessary source code so that end users are able to modify the component. The LGPL does allow other approaches than dynamic linking (such as including the source code for the complete software, even if it's not under a free license). However, all other approaches will likely be more complicated than the standard dynamic linking technique.
Answer: If you make it clear that you are renting only the hardware and the lessee is only allowed to use that device as supplied (i.e. to run, but not to make copies of, any software contained), then the associated copyright licenses and the associated licensing requirements of the software residing on that device are not relevant to you and are not relevant to the lessee.
Why? This is because if you let someone use a physical medium in which software is contained (such as a PC, or some hardware device which contains ROMs with software written on them), copyright law only protects the action of making copies of (or modifying) the software. If the end user only runs the software, or uses it in some normal way, which does not otherwise require a copyright license, then the copyright holder has no right to dictate how a user may use (i.e. run, execute) a piece of software. I.e. copyright law protects only making copies of a work or modifying a work. The GPL goes so far as to point this out explicitly:

Acceptance Not Required for Having Copies.

You are not required to accept this License in order to receive or run
  a copy of the Program. Ancillary propagation of a covered work
  occurring solely as a consequence of using peer-to-peer transmission
  to receive a copy likewise does not require acceptance. However,
  nothing other than this License grants you permission to propagate or
  modify any covered work. These actions infringe copyright if you do
  not accept this License. Therefore, by modifying or propagating a
  covered work, you indicate your acceptance of this License to do so.

Suppose you are a renter of a PC which includes some (L)GPL software. And suppose you do not agree to the terms of the (L)GPL license. According to section 9 of the (L)GPL license itself, you are under no obligation to accept the license requirements in order to use the software in question.
The GPL goes so far as to make the above explicit, but this notice is not actually specific to the GPL. Even if the software were under some other license (e.g. a proprietary license), if no copy is being made (i.e. no propagation is occcuring, and no modification is occuring), then no license is actually required to simply use hardware that happens to contain software which is under copyright.
Comment: Note that, in the EU, [renting is a right protected under copyright law](https://en.wikipedia.org/wiki/Rental_Directive), so the GPL term of propagation includes renting. Also, I am not convinced your first paragraph is true, otherwise I would see that tactic being used much more for (cable/wifi) routers to avoid having to publish the firmware.
Comment: If I were to buy a one year subscription for the commercial licence, and distribute the software (I.e. load it onto one of our rented machines), would I still be able to rent out the computers/software once the licence expires?
Comment: @19172281 You will need to ask the Qt company about that. My understanding is that you need a commercial license to distribute the software for the duration that you distribute the software (unless you are using the LGPL). However for your question's premise, I assumed you are using the LGPL to produce software but are renting a computer which contains it. Whether this counts as "distribution" of the software is unclear to me. My answer says "no" this is not distribution, but if you are doing this in a business or to make money, you need to seek legal advice about the answer for your area.
Comment: @19172281 Another option is to compile your programs statically linked, but then try to comply with the LGPL requirements in another way. For example, you could supply object files and instructions for an end user on how to rebuild your (presumably closed source) application using a different version of Qt. This would appear to satisfy the LGPL license requirements, but I believe in practice this option is never taken.


Do you always need to show statistical significance of results in a paper?

Question: Is it enough to discuss a higher mean in one set of results than another without statistical significance (as long as you are clear that significance wasn't tested)? Can this, in your experience, result in rejection by peer-reviewers?
Comment: You could go ahead and do a rough-and-ready significance test (compute "type A uncertainty estimate" standard error of the mean for each set of results; comment on whether the difference between the means is large or small compared with the larger of the two standard errors), and it would probably take you less time and effort than it did to type this SE question!
Comment: This is something that I never understood. There is a huge number of papers in which errors treatment is simply neglected. Chemistry, material science, applied physics, etc. Including my papers except for some simple regressions or variability windows. Not that I feel we should do different. I guess it depends on the context. Or on the hypothesis to test / compare.
Answer: Of course I can't speak for EVERY journal in the world. Who knows?!? But in principle, a difference in means, without further statistical analysis is 'meaningless'. You are applying a transformation that hides the variance of the underlying data, so it is impossible to interpret if the differences observed are likely due to a different mean of the samples, or due to simply random variation.
In addition, I would argue that if the journal does allow you to publish a difference in means without further analysis, you still shouldn't do it--and probably find a different journal to publish in.
Answer: It is a good idea to avoid meaningless "Null Ritual" statistical tests that give the appearance of statistical rigor, but are often deeply misleading.  For instance, there is no point in performing a test for zero-difference between things that you know a-priori cannot reasonably be expected to be the same.  For example, a test for zero difference in the proportion of journal paper abstracts that express an acceptance of anthropogenic climate change, versus the proportion when judged on the basis of the whole paper, tells you nothing whatsoever.  A non-significant result only tells us that the sample is too small to reveal what we already know.  The space in the abstract is too small to include a statement of whether anthropogenic climate change is happening, unless that is the specific purpose of the paper.    However there is more room in the body of the paper, so it is more likely to contain such a statement in providing context for the findings.  So we would expect the proportion to be somewhat higher in the latter sample.  It certainly does not cast any doubt on the usefulness of the survey of abstracts (in case you are wondering, yes, this is a real example).
If the difference is too small to be of any practical significance, I'd argue that there is no point in performing a test for statistical significance either.
If you are going to claim that X is different to Y based on some data, then you need to perform a test of statistical significance.  However, I'd argue that it doesn't necessarily need to have a significant result for the paper to be worth publishing, providing the conclusions are suitably circumspect (the method/reasoning may be of sufficient interest, even if the results are inconclusive).  The main purpose of statistical significance tests is to enforce a degree of self-skepticism on the part of the researcher, and not much more than that.  It is most useful when it give a non-signifiant result.
Answer: It depends on the situation.
If the mean of one result is obviously much higher than another one, then there is no need to provide statistical significance at least from my point of view.
If the mean is the same or very close to each other, then there is definitely a need to provide statistical significance.
Comment: If it is obvious though, why not perform the test anyway and say "obviously the difference is statistically significant at the X level of significance".  Best not to give hostages to fortune with peer review ;o)
Comment: 'obviously much higher' is a completely meaningless point if the underlying data is unknown. Maybe it's higher because there are a bunch of NA values? Maybe it's higher because there is a small number of samples with huge variance? There is no absolute need to run a statistical test, but at the very least there needs to be a representation of the underlying data/variance and not just two means with one being 'obviously much higher'.
Comment: "if" is doing a lot of work there.  If the underlying data is unknown, then nothing is obvious, but in that case @LGDGODV's  reasonable suggestion doesn't apply anyway.  If I give a comparison of the mean radius of stars and that of rocky planets, then it is obvious that the difference is going to be statistically significant, and it would be a waste of time performing a test of an entirely uncontensious statement.  As I point out in my answer to the question, "null ritual" NHSTs can be misleading as well.
Comment: I agree. I guess depending on the field this is not very welcomed. But I am speaking of facts, like saying the boiling point of X is Y. I am really puzzled myself although I proceed by feeling.


How does the Coupon Collector Problem change when you draw two items at the same time?

Question: If there are 100 tickets in an urn, and you draw two at a time, look at them, and replace them both, how does that change the problem? It would obviously take half as many trials, but how does the fact that one ticket will never be a duplicate of the other affect the result?
Answer: It helps.  The simplest way to analyze is to just say that, for any positive integer $n$, the probability of finishing on or before $n$ rounds of this pairwise selection is greater than or equal to the probability of finishing on or before $2n$ rounds of single selection.
An exact analysis is more complicated but you could define a Markov chain with state $c(t) \in \{0, 1, ..., 100\}$ being the number of coupons you have seen after round $t$ (with $c(0)=0$ and $c(1)=2$).  Then for $c \in \{2, ..., 98\}$:
\begin{align}
P_{c,c+2} &= \frac{{100-c \choose2}}{{100 \choose 2}} \geq \left(\frac{100-c}{100}\right)\left(\frac{100-(c+1)}{100}\right)\\
P_{c, c+1} &= \frac{{100 -c \choose 1}{c \choose 1}}{{100 \choose 2}}\\
P_{c,c} &= \frac{{c \choose 2}}{{100 \choose 2}} \leq \left(\frac{c}{100}\right)^2
\end{align}
and you could formally use the inequalities in a stochastic coupling argument to prove the claim in the first paragraph.
Comment: Alright, I've only *heard of* Markov chains and stochaic anythings, any resources you'd suggest for learning more about them and possibly this type of problem? I'm in over my head.
Comment: You can search the web for "Markov chains."  Above I am using $P_{ij} = P[c(t+1)=j|c(t)=i]$, which is standard notation for Markov chains.  Here are some class notes on expected travel times in Markov chains. http://ee.usc.edu/stochastic-nets/docs/markov-chains-travel-times.pdf


Center of orbit stuck

Question: The center of orbit is stuck on a doughnut. I have tried moving 3d cursor, origin, selecting different objects, tried number-pad period, tried directly clicking frame selected (just puts view in center of doughnut), changing settings (already tried rotate around selection), tried rebooting it. There isn't any other posts with the same question, some are similar, though none completely match and no suggested  solutions have fixed this. You can see in the images, that no matter where the orange dot is, the camera centers around it (even if it is off screen, I lost the whole scene a couple times this way), and everything else is moved. It also appears this does not happen in sculpt window, even in object mode, but in modeling window, in all modes, it has this behavior.
Answer: About 20 seconds after I posted this I realized there was another view options section on the top right side of the view port or it can be accessed with hotkey N. I had pretty much every setting in the view section on the top left hand side, and almost every setting in the navigation and view port sections of the preferences settings. Please discard this question, I am just a beginner and am not used to the interface yet

Center of orbit stuck


How to scale the rendered image in composition?

Question: In order to get rid of noise, I'm rendering using 200% for render Resolution, 512 Render Samples, so I can decrease the size later in Photoshop by 50%, to make anti-aliasing, my question is: Is there a way to do that in Composite, so the final image will be scaled and anti-aliased?
Answer: Yes, Blender can scale in the compositor using the Scale nodes seen below. Pipe the image into a Scale node, then from the Scale node into a Composite output node. If you have "Compositing" checked on in the Rendering tab of the Properties pane, then each frame will be modified and then saved out as usual.

You can also use a File Output node to save out different files in addition to the final Composite, if you want.
Note that in Absolute Mode for the Scale node, you need to input the final image size you're after, not a ratio, so if you want a full HD, you should input 1920 for X, 1080 for Y.
Comment: I tried the Absolute Mode, the input in this mode should be the final size of them image that you want in pixels, for example: 1920 X 1080, uvsing 0.5X0.5 as in the image just ruined the image.
Answer: The Compositor

The Compositor can Scale, Offset and Clip.
Showing Images and Blender Textures ... Scaled and Offset. Viewers.
Split Viewer showing as a background.

A Blender World texture can be sampled in various way including no interpolation, or pixelated.  The Zero Saturation appears in the Compositor.  The non interpolated coarse sampling does not appear in the Compositor.  Coarse sampling pixelation produced by nodes in the Compositor.
Click image to see larger version.
Comment: This answer isn't very descriptive. Could you elaborate?


How do I sync offline data with iOS native app?

Question: iOS native app:: When I refresh remote data using SFSyncStateMergeModeOverwrite sync options the records previously downloaded, that have been deleted in Salesforce, are not removed from my local data.  What do I need to do to sync the local data with Salesforce, including deleting invalid records?
Answer: This question has been answered by Bharath Hariharan in the Mobile SDK community.
Bharath Hariharan
Currently, we don't have a way to determine if a record has been deleted on the server. Hence, the record hangs around in SmartStore.
Arthur Lockrem
What do you suggestion I do if the client wants to get a true sync with Salesforce?  Is there a way to completely clear the local data?
Bharath Hariharan
Due to server side API limitations to detect deleted records, there are 2 possible ways to solve this:
1) Delete all the local data and re-insert all the new records fetched from salesforce via syncdown. This is very easy to do but works only if the data size is small (few hundred records). But for large datasets, this could be a big performance hit.
2) The other option is to scan the local store and compare the ids from local store and salesforce db. This can support larger datasets but gets more complicated to implement as the data size grows.
Arthur Lockrem
That is great advice.  Thank you.
Please confirm the SFSmartStore removeEntries:fromSoup: is the proper way to completely clear the local data.
If this is the right method, I assume running this in a loop is the proper way to delete all entries in multiple soups.
Thank you for all of your help.
Bharath Hariharan
If you're attempting to remove specific entries, then yes 'SFSmartStore removeEntries:fromSoup:' is the way to go. If you're attempting to remove ALL entries from a soup, 'SFSmartStore clearSoup:' is the way to go.
Read more
Arthur Lockrem
Perfect!  Thank you again.


Collate view with old record on couchdb

Question: I need to create a collate view with couch db but I dont want to use the current records, I want to use records of a specific revision. For example, lets imagine that I have an invoice with an array of products ids (and theirs revision), I want to return the products with the description and prices as was at the invoice creation.
Answer: Normally you should never do so because other revisions may be deleted after compacting the database.
You should include all necessary fields to recompose(reprint) the invoice in the invoice document, like: product description, product price, total, and so on.
This is the same if you would store invoices in a rdbms.

Collate view with old record on couchdb


Power set of a set containing a set

Question: I need some help understanding this concept a little better. I understand the general power sets, but only worked nice and easy examples where only the set consisted of only single elements like $\{a,b,c\}$. I can do that power set, but I am confused on the power set of a set containing a set. The problem I am trying to work is $\{a,\{a,b\}\}$. Typically when you have a set $\{x,y\}$ the power set is $\{\{x\},\{y\},\{x,y\}\}$ so would this problem be similar to that where $\{y\}=\{a,b\}$? Or would I then need to perform a second power set on the inner set?
Comment: What are you trying to prove?  There's nothing stopping you from defining a set that itself contains single elements, as well as sets, as long as it doesn't violate the ZFC axioms.  What's the problem?
Answer: Let $X=\{a,\{a,b\}\}$. The set $X$ has two elements: nothing more, nothing less. Then,
$$\mathcal P(X)=\big\{\emptyset,\{a\}, \{\{a,b\}\}, \{a,\{a,b\}\}\big\}$$
If things don't become clear, you can try "encapsulating" the element $\{a,b\}$ calling it $c$, so you can now write $X=\{a,c\}$.
Comment: I tried encapsulating and that did help out! Thanks a lot!
Answer: Actually you are not completely right when you compute the power set of $\{x,y\}$:
The power set of $\{x,y\}$ is $\{\emptyset, \{x\},\{y\},\{x,y\}\}$ i.e the empty set is always included as it is a subset of any set.
If you have the set $A = \{a, \{a,b\}\}$ and want to compute the power set, we need to find all subsets of $\{a,\{a,b\}\}$.
The power set must have $2^2$ elements as there are 2 elements of the set.
What are these elements?
$\emptyset$ is always an element, so we include that one
$\{a\}$ is another subset as all its elements are in $A$.
Same reasoning applies to $\{\{a,b\}\}$ as $\{a,b\}$ is an element in $A$.
Finally $\{a,\{a,b\}\}$ is a subset as the entire set is always a subset.
Final powerset $\mathcal{P}(X) = \{\emptyset, \{a\}, \{\{a,b\}\},\{a,\{a,b\}\}\}$
Comment: Okay that makes sense. Yeah after looking back I realized I forgot the empty set, I just don't know the character code for it. Thank you for the help!

Power set of a set containing a set


How to download HTML using PHP?

Question: How do I download an HTML file from a URL in PHP, and download all of the dependencies like CSS and Images and store these to my server as files? Am I asking for too much?
Answer: The easiest way to do this would be to use wget. It can recursively download HTML and its dependencies. otherwise you will be parsing the html yourself. See Yacoby's answer for details on doing it in pure php.
Answer: I would recommend using a html parsing library to simplify everything. Namely something like Simple HTML DOM.
Using Simple HTML DOM:
$html = file_get_html('http://www.google.com/');
foreach($html->find('img') as $element){
    //download image
}

For download files (and html) I would recommend using a HTTP wrapper such as curl, as it allows far more control over using file_get_contents. However, if you wanted to use file_get_contents, there are some good examples on the php site of how to get URLs.
The more complex method allows you to specify the headers, which could be useful if you wanted to set the User Agent. (If you are scraping other sites a lot, it is good to have a custom user agent as you can use it to let website admin your site or point of contact if you are using too much bandwidth, which is better than the admin blocking your IP address).
$opts = array(
  'http'=>array(
    'method'=>"GET",
    'header'=>"Accept-language: en\r\n"
  )
);

$context = stream_context_create($opts);
$file = file_get_contents('http://www.example.com/', false, $context);

Although of course it can be done simply by:
$file = file_get_contents('http://www.example.com/');

Answer: The library you want to look at is cURL with PHP. cURL performs actions pertaining to HTTP requests (and other networking protocols, but I'd bet HTTP is the most-used.) You can set HTTP cookies, along with GET/POST variables.
I'm not sure exactly if it will automatically download the dependencies - you might have to download the HTML, parse out the IMG/LINK tags, and then use cURL again to fetch those dependencies.
There are a bazillion tutorials out there on how to do this. Here's a simple example (scroll to the bottom) for a basic HTTP GET request from the people who make libcurl (upon which PHP's cURL bindings are based):
<?php
//
// A very simple example that gets a HTTP page.
//

$ch = curl_init();

curl_setopt ($ch, CURLOPT_URL, "http://www.zend.com/");
curl_setopt ($ch, CURLOPT_HEADER, 0);

curl_exec ($ch);

curl_close ($ch);
?>

Answer: You might take a look at the curl wrappers for PHP: http://us.php.net/manual/en/book.curl.php
As far as dependencies, you could probably get a lot of those using some regular expressions that look for things like

How to download HTML using PHP?


Is it possible to send data through I2C with TIM without CPU interrupt and just DMA Interrupt

Question: Because I've seen HAL_TIM_Base_DMA_START() in the STM32F7 HAL timer library, I though maybe it is possible to, for example, call HAL_TIM_Base_DMA_START() and timer continually requesting DMA to transmit data to I2C preiodically without CPU activity?
Comment: What would this achieve? The I2C HAL can already use DMA to do I2C data transfers without CPU intervention (after the transfer is properly set up, that is).
Comment: @Justme But you must call it, but with timer you even don't need to call it, since it will be autocalled periodically and precisely.
Comment: To put things in context, you have a 480 MHz MCU, and the highest raw I2C speed is 1 MHz tops. A byte is transferred at 111 kHz rate. You can use standard polling, interrupt or DMA interface. If the device you want to communicate with stretches the clock to slow down transfers, then your forced DMA will not work. It just makes no sense to use timer events to manually trigger I2C DMA transfers. Even if it is possible.
Comment: @Justme ie MCP4725 doesn't slow by stretch and DMA will work, but higher speed will cuse it to not work them manually must be care of speed control of timer.
Answer: No, because how would the timer know anything about how to control the I2C peripheral to do something over a DMA channel. At most you can send bytes at a certain rate by triggering a DMA transmission by using a timer but the I2C transaction needs to be preconfigured to that point beforehand.
I2C transactions do support DMA and you can use timer interrupts to start I2C transactions which can do the transmission of the data phase with DMA in the background.
Comment: You could maybe send the start/adress then transmist other block without start and stop by timer to ... , for example fast ADC?
Comment: In theory, if you want, you can do it as explained in my answer. The point is, even if possible in theory, there is no practical use case. You have a 480 MHz CPU and max transfer rate of 111 kilobytes per second, with the overhead of the bytes needed to address something in a chip.
Comment: My effort is not to maximize communication throput but is to maximize CPU processing power.
Comment: If you already are afraid that I2C takes too much CPU time even with using standard DMA transfers initiated by I2C peripheral, it means you already have the wrong CPU.
Answer: Well - you could configure a timer to trigger a DMA to write bytes to the I2C peripheral - but it's unlikely that this would result in anything useful.
A successful I2C transaction requires Start & Stop conditions, possible Restarts, often Ack checks, etc - none of which would easily be managed with just timer-driven DMA sending bytes to the I2C.
You could configure a Timer such that its interrupt begins the I2C transaction (sends the Start bit) and gets it running to the point where you now only need to send a block of data, and then configure the DMA to send that data to the I2C peripheral ,- but you wouldn't involve the timer there - you would configure the I2C peripheral to trigger the DMA directly whenever it's ready for a new byte.
Then at the end you'd need to complete the transaction by sending a Stop bit, probably triggered by the DMA interrupt telling you that the data block is complete.
Comment: You could maybe send the start then transmist other block without start and stop by timer to for example fast ADC?
Comment: What does it buy you to use the timer to trigger the DMA to copy a byte to the I2C when you could just have the I2C trigger the DMA directly whenever it needs a new byte to send?
Comment: Everytime we need to send adress. At least we need to think about it to where to place it's trigger in main app or in timer. But by timer+adc it will become quiet. Also I2c was an example. in this way we can have stable constatnt speed communication through DMA. But we must be aware that everything have both pros and cons.
Comment: Sure, using a timer will give you a consistent period between one byte and the next, but that is very rarely a requirement in I2C communication. I've been doing this for decades and have never yet come across a project where that would have been needed.
Comment: I could imagine a case where maybe your microcontroller has a silicon bug preventing you from triggering the DMA directly from the I2C - maybe there you could use a timer to trigger the DMA instead ...
Comment: The you mean this is possible? do you know how to implement it? maybe that is not usefull in many application but if your processor have lot to do, maybe decreasing even one line of code will relax it more, and managing something also. thanks. Also using DMA for send one byte by CPU and others by DMA seems to be inefficient in the purpose I mean.
Answer: It seems it's possible using DMA request generator.


Is this translation request off-topic here?

Question: This question Kiel traduki Esperante tiun ĉi ludkarton? requests a translation of the text of a playing card, not any specific word or phrase. Is it outside the topic for this site?
Comment: I suppose it is okay since we aren't overwhelmed in questions atm. But this question does have lower reuse value compared to others as @kiamlaluno said.
Answer: I understood the question to be "how do you translate the name of this monster" - which I chose not to answer but for other reasons. I do think it's essentially off topic and if our community is to have any value, we will come up with some guidelines about this.
Answer: I would consider it off-topic for the fact of asking how to translate in Esperanto a name of an imaginary creature that is not even as common as dragons, griffins, or unicorns.
It is an invented word created specifically for a playing card game, and I don't feel the question is going to help future users.