Why aren't links clickable on my 404 error page?

Question: I have created a custom 404 error page. However, the links are not clickable. The link to my site and a random 404 page is https://createandgo.com/error404page
Comment: Because you have a giant giphy embed sitting on top of them that's broken ( as in it won't load ), and broken ( as in it has position relative and zero height and a few other styling related issues ). You also have CSS styles that hide giphy embeds on 404 pages too. Check it in your browsers dev tools and you'll see this is a generic CSS issue
Answer: It's because you have incorrect css being used on some divs within that page.
On that page a couple of divs down from the H1 deceleration you have a div with some inline css:

You need to remove the padding-bottom:56%; so it is:

Then in you have some css on in that template inside the  tags of:
.above {
    margin-top: -580px;
}

You also need to remove that completely. Once you do that your issue will be gone and your content will be positioned properly.
Comment: Thanks, this worked! Unfortunately, my rep score isn't high enough to upvote.
Comment: Hi Daniel, that's great news   :) No worries.
You should be able to accept this as answered. You do not need to up vote it    ;)


yammer js sdk issues

Question: We are experiencing the following error when accessing Yammer API.
JQMIGRATE: jQuery.parseJSON requires a valid JSON string
platfor..._sdk.js (line 31)
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://www.yammer.com/api/v1/suggestions.json. This can be fixed by moving the resource to the same domain or enabling CORS.
Ref:
Yammer JS SDK — problems with CORS
Here, it is said that the issue is resolved. But we are still facing the issue. Please confirm if the issue is resolved.
Best regards,
Parameswaran.
Answer: When using the Yammer JS SDK you'll need to reference api.yammer.com instead of www.yammer.com/api/v1.
Or better yet, if you want to clean up the url you can omit the protocol, domain, and extras (/api/v1) and include the REST resource (suggestions in your case) and the output format (json).  See example below:
<code>yam.getLoginStatus(
  function(response) {

   if (response.authResponse) {
      console.log("logged in");
      yam.platform.request({
        url: "suggestions.json",     //this is one of many REST endpoints that are available
        method: "GET",
        data: {    //use the data object literal to specify parameters, as documented in the REST API section of this developer site
          "letter": "a",
          "page": "2",
        },
        success: function (user) { //print message response information to the console
          alert("The request was successful.");
          console.dir(user);
        },
        error: function (user) {
          alert("There was an error with the request.");
        }
      });
    }
    else {
      alert("not logged in")
    }
  }
);
</code>

yammer js sdk issues


"One is done for you" or "One has been done for you"?

Question: While I was writing a textbook I gave an exercise for students. Since the exercise was difficult, I gave an example and gave the instruction

One (example) is done for you

The editor corrected it as

One has been done for you

I would like to know whether my instruction "one is done for you"
is wrong or not.
I have referred to many textbooks and found both constructions. Later, I consulted a famous linguist who told me that both are correct but had a difference in meaning. The linguist was Rod Mitchel whom  I consulted on LinkedIn. He gave an elaborate explanation which I now forget and the link is broken. I can remember only vaguely.
The first one means the example is ready for you. You can have a look at it if you like.
The second one means I have taken care to give an example for you and you can do the exercise with its help.
I hope you would be kind enough to answer my question
Answer: As sentences, both are perfectly grammatical. In the context of pre-completed exercises in a textbook, though, "has been done/completed" would be more common, stressing the perfective aspect of the action, so I would agree with your editor here.
Credit: Janus Bahs Jacquet
As Janus says, both are grammatical. The difference in meaning is negligible for just about anyone not writing a treatise on English grammar (focus totally on the completed example ('is') vs focus rather more on the anonymous agent). I'd expect to see '... one is done for you' in the formal, erudite, rather stuffy old textbooks that I was exposed to 55 years ago and the more natural-sounding 'one has been done for you' in modern treatments: this is really just a style issue for the vast majority of people.
Credit: Edwin Ashworth

“One is done for you” or “One has been done for you”?


How to retrain the neural network when new data comes in?

Question: I am new to deep learning. Can anybody help me with the online learning implimentation for deep learning models. As per my understanding, i can save a keras/tensorflow model after training and when new data comes in, i can reload the network back and retrain the network using the new data. I haven't seen anywhere documenting this method. Is my understanding incorrect? If yes, let me know what can be done so that the model keeps on getting retrained when new data comes in?
Answer: Yes, there is some methods to do this based on the library. The proper keyword for this functionality is Checkpoint. Hence, you can check functions to save or restore the checkpoints from hard disk to continue learning or prediction in a new session. For example you can see the following in Tensorflow:

The tf.train.Saver class provides methods for saving and restoring models. The tf.train.Saver constructor adds save and restore ops to the graph for all, or a specified list, of the variables in the graph. The Saver object provides methods to run these ops, specifying paths for the checkpoint files to write to or read from.

For more details about this in Tensorflow, you can follow this link.
To complete the case you can follow this subject in another library such as CNTK in this link.
Answer: Its extremely simple. There are a lot of ways of doing it. I am assuming you are familiar with Stochastic Gradient Descent.  I am going to tell one naive way of doing it.

Reload the model into RAM.
Write a SGD function like SGD(X,y). It will take the new sample and label and run one step of SGD on it and save the updated model.
As you can see this will be highly inefficient, a better way is to save a number of samples and then run a step of stochastic batch gradient descent on it. So that you dont have to reload the updated model every time you give it a new sample.

I hope this gives you a rough idea of how the implementation can be done. You can easily find much more efficient and scalable ways of doing this. If you are not familiar waith algorithms like SGD, I would recommend to get familiar with them because online learning is just a one sample mini batch gradient descent algorithm.
Answer: Having more data may not mean that you have online learning.
Above answers are correct if you assume that the coming new data samples will not have any concept drift. Meaning the true data generating distribution may change in a way that your current ( most recent model) is in a point that is very far away from the optimal minimum for the new data distribution.
I recommend you to read more about "concept drift" and understand if your data will have any concept drift.
Try to search for how NN deals with concept drifts. Unfortunately I am not aware of any technique or method can make NN adapt to concept drift.
If you do not expect any concept drift, then saving the check point and continue training will be good solution if you are using stochastic gradient descent


Subscribe/rss tag hover annoyance

Question: The new "death-star" styled "subscribe" hover popup (when you mouseover a tag): Does it really need to show us that it's loading? It doesn't bring any benefit, and to me mild irritation. Can it not be shown once the content has arrived rather that blatting the page with a big black stripe of pointlessness until the AJAX request has caught up? Perhaps loading might be demonstrated in a less intrusive manner. It's really rather visually disturbing for such a (to my mind) low priority feature. I think it's the 2-stage delivery that grinds the most.
Comment: I'd rather have a way to completely disable the entire inane popup. Anyone good with GreaseMonkey?
Comment: If you click a tag soon after mouseenter, you get a hovering black rectangle of nothing before the linked page loads. It looks awful.
Answer: The benefit that it brings is it shows an indication that something is happening in response to your action of mousing over a tab.  While the actual content appears essentially immediately for me, on a slow connection it would be counter-intuitive for there to be no loading indicator.  It would be very frustrating to mouse over a tag and have nothing happen only to have it appear in a disjointed manner.
Comment: I concur that it's important that there is notification of the loading state, however I think the delivery of that notification is visually disturbing (especially because of the high contrast of the popup) and wonder whether it could be delivered in a less intrusive fashion.

Subscribe/rss tag hover annoyance


How do you remove Facebook birthday from "My Calendars"?

Question: My calendar is full of facebook friend birthdays! and worse, they are listed under "My Calendar", not Facebook calendar, so I can't hide them by unchecking Facebook in Calendar, Settings > Calendars. Even thouh they are listed under My Calendar, they still have facebook logos on the entry and a sync logo. I tried by turning off the sync option, but they are still there. How can I remove them from my calendars, and add them to the "facebook" calendar?
Comment: I have the same issue with a Facebook event I accepted by mistake, can't get rid of it off my calendar either. Even although I've removed it in Facebook.
Comment: birthday is worse because it makes your calendar really full, lol.
Comment: How did they get there to begin with?  Via the official Facebook app or something else?
Comment: I think it must have gotten there from built-in account sync. I can remove my facebook account and check whether they still remain, but I'm a bit reluctant to do this because 1) it will mess with my contacts and 2) I'm not sure whether the birthday will really be removed when I do that.
Comment: i have all my FB birthdays on my Google calendar TWICE.  I have a Sprint Samsung Epic.  Any thoughts?  I don't want any FB birthdays on my Google Calendar at all.
Answer: This was reported in the Android Central forum here with a link to LifeHacker. It sounds like it will allow you to sync your Facbook calendar without the birthdays because you're exporting the events directly from Facebook. First, you may want to undo the sync that you have going on now. Hope it helps.
Quoting the post from Android Central:

just go to your google
  calendar thats linked with your google
  account on your phone and then follow
  this article.
Add Your Facebook Events to Google
  Calendar

In Facebook, go to your EVENTS page.
At the top of that page click EXPORT EVENTS
You'll get a pop up window with a URL, copy it.
In Google Cal, on the bottom left you'll see 'Other Calendars' and below
  that a link to ADD. Click ADD
One of the new options you'll be presented with is ADD BY URL, select
  that
Paste the URL from Facebook where it asks for it.

and thats it! when your phone calendar
  syncs with your google calendar, all
  your facebook events will show up too
  and no birthdays.
Comment: I awarded the bounty because it's about to expire and I dont want to just lose 50 rep to the air :D but still the issue is not solved :(
Comment: the problem is that the birthdays show up as entries from "My Calendar", not as a Facebook event (they still have facebook logos on the entry and a sync logo though). I unchecked Facebook from calendar sync setting but still the birthday show up in the calendar.
Comment: It may be because the birthday's are syncing through the Contact Sync, then syncing from your contacts to your calendar.
Comment: @matt: how to cancel that?
Comment: @Louis I wanted to earn that bounty so I added Facebook to accounts that sync, then added FB to the calendar. Birthdays only show up when I have a the FB calendar added. Like @Matt suggests, it could be something other than FB that's causing this. Trying playing around with which accounts are synced. Go to Settings > Accounts & Sync (or something like that).
Answer: Go into Accounts and sync in Settings and remove Facebook HTC Sense and your calendar will be back to normal. Stupid thing had my calendar full of birthdays from my Facebook that I don't really care about....
Answer: There is a downward-pointing arrow on the top right of of the calendar. Hit this, and a list of all your calendars drops down. Untick the ones whose events you don't want synched to your phone's calendar.
Answer: I simply stopped syncing the Sense Facebook app to fix this.  However, all the contacts I connected with Facebook are gone as well which is the down side.


Difference between Description & Short Description

Question: What's the difference between Description & Short Description Magento Backend. Whether we need to fill both the column in Magento Backend panel while adding the listing the new products?
Answer: those are 2 product attributes. and are not connected in any way. Meaning the short description is not generated for the description.
some pages (e.g. product-detail-page) show the description and some pages (e.g. catalog-product-listing) show the short description
Answer: Product "Description"
This is the body of the product details on the product page. Here you can put all the details that will describe your product. All the information you put there will be displayed on the details tab.
Product "Short Description"
This is up to you if you want to utilize this one. It is displayed most of the time together with the product like a unique excerpt. Typically, you can use a few words or sentences to more descriptively define the product for customers in this field.
Answer: Adding to the above answers. For every attribute, there is an option "Values Required" to control the mandatory check. If it is set to yes then the field will change to mandatory. So, it depends on the settings you have in your project.
To identify easily you will find a red asterisk mark which indicates that the filed is Mandatory. Here is a sample screenshot.

In order to change the option go to Select Stores > Attributes > Product. You will list of attributes, filter the attribute you want, select it and in the next screen you will see "Attribute Information" section > Properties  > Attribute Properties change the  "Values Required" option
Comment: Hope this answers your question. If so, please do upvote and accept it as answer


Expression/term for space between door and floor/wall

Question: Let's say smoke is escaping through a close door. It would be escaping through the space between the door and the floor or the wall, or perhaps between door and the jamb. Is there a term for that? Or is there an expression for that (perhaps: smoke seeping through the door? but that would suggest that it goes through door, rather than the space between the door and the floor or jamb).
Comment: In contradiction to an earlier comment, I would completely understand what *smoke coming **through** the door* meant. It's used on a fairly regular basis, in my experience. It's not *literally* true, but that doesn't matter.
Comment: As you say, smoke does not seep through the door. It seeps through the *doorway*. And it *seeps* because the door itself is closed. If it were open, then smoke would *pour* or *billow* through the doorway.
Comment: @WeatherVane Yes, but despite the door being closed, the smoke still escapes through the gaps, because the door is not airtight. Is there an expression for that?
Answer: Door gap is the general name for all of the gaps around the door.

The best method for measuring door gap dimensions is to use a tool of the appropriate thickness that can be inserted  between  the  door  frame  and  door,  the  door  and the floor, and between opposing vertical edges (aka, meeting stiles) of paired doors.  (Doorgapgauge.com, emphasis added)

At idighardware.com, the sdi fact file is quoted, calling the gap at the floor

FLOOR CLEARANCE:  The distance between the bottom of the door and the top of the material directly below the door. This varies with applications, such as concrete, any floor covering and/or a threshold.

This gap is also called bottom clearance, and the top gap is called head clearance, while the side gaps are called stile clearances at taylordoors.com.
To class them all together, you could say "The smoke is seeping through the door gaps."
Comment: I have no idea why someone downvoted your answer. Door gap and door clearance are just right. +1
Comment: Consider *crack*.
Answer: I can't find anything shorter than a long  phrase:

smoke stream/ing/ed/ in through the chinks of the door where it meets the frame.


Will Canadian Motion Controller work in EU PS3?

Question: I have a European PS3 but I'm going to Canada in a couple days and wanted to know if the motion controllers from US will work on my PS3. They are A LOT cheaper there and in Portugal is nowhere easy to find them available to buy used...
Comment: They use bluetooth.  That's a universal standard.
Comment: The technology for controllers should be the same regardless of region.  I wouldn't see why not.
Comment: I don't really know how the controller communicates with the console to detect the button presses. The frequencies could be different...
Answer: Based on my knowledge there is no difference in hardware devices, since we're not talking about the power supply or different tech standards like in mobile phones/networks. Therefore I guess you won't have any problem to get your PS3 to work with this device.
If you buy a new one from a shop keep in mind that you may have some trouble with the  sending in for repair.
Comment: and what about the communication frequencies? It could be different, no?
Comment: I thought that the regular gamepads communicate via bluetooth and so should the move-pad. Why should sony change this and further more, why should sony produce so many different devices for each country? You can change the powersupply easily, but the technology inside a gamepad? I don't think so, but I'm not *that* into sonys hardwareconcept :)


How to use LOF for outlier detection as I have training and test dataset?

Question: I want to use the Local Outlier Factor (LOF) algorithm for outlier detection but it simply finds outliers on unlabed data as whole and you do not need to have a training and test set. However in my case I expect to get some knowledge from the training set and test this knowledge on test data (it seems like an ordinary classification problem :) ). Is there any way to use the LOF or any other anomaly detection algorithm via training and test set? At least, how can I get some statistics for my test set specifically? What is the methodology of using these with separated data?
Comment: how are your test/training set constructed? For example, are they random partition of the same dataset or are they coming from two temporally disjoint datasets (e.g. the test set is composed of observations samples before a certain date and the train set of observations after that date)?
Answer: If you have training data, you might want to look at one-class classification methods, such as one-class SVM.
Answer: You can try this paper [1]. This work is about matching train and test distribution matching and estimation of density ratio $P_{test}(x)/P_{train}(x)$. However, it is designed in such a way that instead of computing the density ratio of train to test, it computes density ratio of train to some convex combination of train and test distribution i.e $\alpha P_{train} + (1 - \alpha)P_{test}$. Now, by setting $\alpha$ close to 1, they are able to do outlier detection and in fact it is one of their experiments in their paper.
Now, this method does not use the training set labels, but just the training set points. As @Anony-Mousse has already pointed above (+1), you can also try out one-class SVMs for the same as well, which can use the labels.
[1] Relative Density-Ratio Estimation for Robust Distribution Comparison
Paper: http://arxiv.org/abs/1106.4729
Matlab code : http://www.kecl.ntt.co.jp/icl/ls/members/myamada/RuLSIF.html
Answer: The answer is no, LOF is not appropriate for your problem. LOF is an unsupervised outlier detection method. Now, the features you select and the distance metric you pick for your graph naturally determine part of what it means for a point to be further from its neighbors than they are from each other, but at the end of the day, what you need to do is just train a good ol' supervised classifier. Someone suggested SVM, you might also look at boosted trees, random forest, neural nets, logistic regression, etc.


homework questions

Question: Speaking as a schoolteacher, I think we should not be so quick to shut down people who come asking for help with homework questions. Registering on this site and asking a question shows a level of initiative, greater than someone who only visited Wikipedia anyhow. Young people who do this are likely to have better things to do than swallow the FAQ before they post. Thoughts?
Answer: I'm not opposed to students asking for help on homework. But I do think that reading a reference (even Wikipedia) to learn for yourself, is in fact showing far more "initiative" than simply and lazily asking random strangers to answer their homework for them.
As far as I've seen, questions that get closed as "homework questions" are typically nothing more than a verbatim copy-paste of the actual essay topic with some variation of "halp" attached to the end. I can't say I see anything wrong with closing those. What we could do, and in many cases this is what members have done, is offer suggestions on how to approach their homework question.
Extending on this, we can supplement these by encouraging homework question posters to ask about individual specific facts in separate questions instead. I don't think this would really do much though. Based on what I have seen so far, people who asked in such a manner tend to not bother spending any more effort on here.
Ultimately, it is worth remembering that there are many other questions that have not been closed. Any of those could have also been asked by students. In fact, some explicitly are.
Comment: Yes, but at the moment we have an explicit rule against asking for help with homework, right? Is that helpful? I meant that asking here is better than wikipedia because a good student knows that wikipedia contains a dangerous mix of highly valuable information and total rubbish, and it's very hard to sort the two out.
Comment: @NeMo There is no such rule as far as I'm aware. Your comment is the first time I've ever seen one invoked in the 555 days I've been here. I do believe Physics.SE has banned homework, but not here at History - if there ever was such a ban, it has long since fallen into desuetude.
Answer: Interesting point.  I don't want to automatically repulse students.
I think we could do a better job of documenting why we don't want homework questions.  In My Opinion: Homework questions are frequently phrased to be valuable to the teacher in assessing whether the student understood an instructional rubric.  Without that rubric, the question is of limited value.  People outside that class cannot fully understand the question.
Any arbitrary visitor to our site should be able to understand the question and the answer without reference to an classroom experience.
I must disagree with you on the FAQ.  Everyone should be accountable for the material in the FAQ.  The FAQ sets out the community standards and guidelines. Reading the FAQ indicates respect for community standards, ignoring the FAQ indicates a disregard for the time, attention and efforts of others.

example -
Answer: To echo what Semaphore said, the problem with homework questions is that they invariably show no prior research and are simply students typing in a question from a problem set and hoping someone else will type back an answer they can copy. This is completely unacceptable and against the principles of the site, not to mention a violation of (Western) scholastic ethics and standards.

homework questions


Using Kaggle Datasets in Google Colab

Question: Is it possible to use any datasets available via the kaggle API in Google Colab? I see the Kaggle API is used in this Colab notebook, but it's a bit unclear to me what datasets it provides access to.
Answer: Step-by-step --

Create an API key in Kaggle.
To do this, go to kaggle.com/ and open your user settings page.

Next, scroll down to the API access section and click generate
to download an API key.

This will download a file called kaggle.json to your computer.
You'll use this file in Colab to access Kaggle datasets and
competitions.
Navigate to https://colab.research.google.com/.
Upload your kaggle.json file using the following snippet in
a code cell:
from google.colab import files
files.upload()

Install the kaggle API using !pip install -q kaggle
Move the kaggle.json file into ~/.kaggle, which is where the
API client expects your token to be located:
!mkdir -p ~/.kaggle
!cp kaggle.json ~/.kaggle/
Now you can access datasets using the client, e.g., !kaggle datasets list.

Here's a complete example notebook of the Colab portion of this process:
https://colab.research.google.com/drive/1DofKEdQYaXmDWBzuResXWWvxhLgDeVyl
This example shows uploading the kaggle.json file, the Kaggle API client, and using the Kaggle client to download a dataset.
Comment: This is awesome @bob-smith, I just made a quick one-liner for the code on colab:
`!if [ ! -f ~/.kaggle/kaggle.json ]; then python "from google.colab import files \n files.upload()" && mkdir -p ~/.kaggle && cp kaggle.json ~/.kaggle/ && chmod 600 ~/.kaggle/kaggle.json; fi`
Comment: Last two part is not working properly for me.

For the second last part (Downloading) getting this:
Downloading stack-overflow-2018-developer-survey.zip to /content

For the last part getting this:head: cannot open '/root/.kaggle/datasets/stackoverflow/stack-overflow-2018-developer-survey/survey_results_public.csv' for reading: No such file or directory
Comment: You can make it secure by changing permissions  `!chmod 600 /root/.kagglekaggle.json`.
Answer: You should be able to access any dataset on Kaggle via the API. In this example, only the datasets for competitions are being listed. You can see that datasets you can access with this command:
kaggle datasets list

You can also search for datasets by adding the -s tag and then the search term you're interested in. So this would give you a list of datasets about dogs:
kaggle datasets list -s dogs

You can find more information on the API and how to use it in the documentation here.
Hope that helps! :)
Comment: You will have to re-download the data every time your VM restarts (just like reinstalling packages). So if it disconnects & reconnects really quickly you shouldn't need to re-download the data. But if you get a new VM, like after 90 minutes of inactivity, then you'll need to re-download that data.
Comment: @hdiz: you can use `!df -h` to find out how much free space there is on the disk.
Comment: Thank you very much, it was very helpful!
Comment: one more question : if colab notebook disconnected or any other reason happen like dead time of VM for notebook arrived , in this situation, should i redownload dataset again or not ?
Comment: does it have a size as big as what realy dataset is , or google just download specific things for using that dataset ?
Comment: That I don't know, sorry.
Answer: Detailed approach:

Go to my account in your profile

Scroll down, until you find an option Create new Api Token, this will download a file called kaggle.json

Go to Colab upload the file kaggle.json

pip install kaggle

create a new folder named kaggle, copy kaggle.json into the kaggle folder, and set read-write permissions only for you(user).

6.Go to Kaggle website.For example, you want to download any data, click on the three dots in the right hand side of the screen. Then click copy API command

Go to colab, paste the API command

8.When you do an !ls, you will see that our download is a zip file.

To unzip the file  use the following command

Now, when you do !ls you'll find our csv file is extracted from the zip file.

To read the file perform a simple pd.read_csv, import pandas

12.As you see, we have successfully read our file into colab.

This downloads the kaggle dataset into google colab, where you can perform analysis and build amazing machine learning models or train neural networks.
Happy Analysis!!!
Comment: This should have been the correct answer. I did not know how to perform the step 7, and kaggle listed only a few datasets with list command. I did not know how download a dataset after finding it in kaggle website since almost all of them are not listed by "datasets list" command. Thanks.
Answer: Combined the top response to this Github gist as Colab Implementation. You can directly copy the code and use it.
How to Import a Dataset from Kaggle in Colab
Method:
First a few things you have to do:

Sign up for Kaggle
Sign up for a competition you want to access data from (for example LANL-Earthquake-Prediction competition).
Download your credentials to access Kaggle API as kaggle.json

# Install kaggle packages
!pip install -q kaggle
!pip install -q kaggle-cli

# Colab's file access feature
from google.colab import files

# Upload `kaggle.json` file
uploaded = files.upload()

# Retrieve uploaded file
# print results
for fn in uploaded.keys():
  print('User uploaded file "{name}" with length {length} bytes'.format(
      name=fn, length=len(uploaded[fn])))

# Then copy kaggle.json into the folder where the API expects to find it.
!mkdir -p ~/.kaggle
!cp kaggle.json ~/.kaggle/
!chmod 600 ~/.kaggle/kaggle.json
!ls ~/.kaggle

Now check if it worked!
#list competitions
!kaggle competitions list -s LANL-Earthquake-Prediction

Answer: Have a look at this.
It uses official kaggle api behind scene, but automates the process so you dont have to re-download manually every time your VM is taken away. Also, another issue i faced with using Kaggle API directly on Colab was the hassle of transferring Kaggle API token via Google Drive. Above method automates that as well.
Disclaimer: I am one of the creators of Clouderizer.
Answer: After the steps (1-6) above from Bob Smith's answer, to use dataset from a particular competition in colab,
you can use the command:
!kaggle competitions download -c elo-merchant-category-recommendation

Here, elo-merchant-category-recommendation is the name of the competition.
Answer: First of all, run this command to find out where this colab file exists, how it executes.

!ls -d $PWD/*
It will show /content/data  /content/gdrive  /content/models
In other words, your current directory is root/content/. Your working directory(pwd) is /content/. so when you do !ls, it will show data gdrive models.
FYI, ! allows you to run linux commands inside colab.
Google Drive keeps cleaning up the /content folder. Therefore, every session you use colab, downloaded data sets, kaggle json file will be gone. That's why it's important to automate the process, so you can focus on writing code, not setting up the environment every time.
Run this in colab code block as an example with your own api key. open kaggle.json file. you will find them out.
# Info on how to get your api key (kaggle.json) here: https://github.com/Kaggle/kaggle-api#api-credentials
!pip install kaggle
{"username":"seunghunsunmoonlee","key":""}
import json
import zipfile
import os
with open('/content/.kaggle/kaggle.json', 'w') as file:
    json.dump(api_token, file)
!chmod 600 /content/.kaggle/kaggle.json
!kaggle config path -p /content
!kaggle competitions download -c dog-breed-identification
os.chdir('/content/competitions/dog-breed-identification')
for file in os.listdir():
    zip_ref = zipfile.ZipFile(file, 'r')
    zip_ref.extractall()
    zip_ref.close()

Then run !ls again. You will see all data you need.
Hope it helps!
Answer: To download the competitve data on google colab from kaggle.
I'm working on google colab and I've been through the same problem. but i did two tings .
First you have to register your mobile number along with your country code.
Second you have to click on last submission on the kaggle dataset page
Then download kaggle.json file from kaggle.upload kaggle.json on the google colab
After that on google colab run these code is given below.
!pip install -q kaggle
!mkdir -p ~/.kaggle
!cp kaggle.json ~/.kaggle/
!chmod 600 ~/.kaggle/kaggle.json
!kaggle competitions download -c web-traffic-time-series-forecasting

Answer: A quick guide to use Kaggle datasets inside Google Colab using Kaggle API
(1) Download the Kaggle API token.

Go to "Account", go down the page, and find the "API" section.
Click the "Create New API Token" button.
The "kaggle.json" file will be downloaded.

(2) Mount the Google drive to the Colab notebook.

It means giving access to the files in your google drive to Colab notebook.

from google.colab import drive
drive.mount("/content/gdrive", force_remount=True)

(3) Upload the "kaggle.json" file into the folder in google drive where you want to download the Kaggle dataset.

(4) Install Kaggle API.
!pip install kaggle

(5) Change the current working directory to where you want to download the Kaggle dataset.
%cd /content/gdrive/MyDrive/DataSets/house_price_data/

(6) Run the following code to configure the path to "kaggle.json".
import os
os.environ['KAGGLE_CONFIG_DIR'] = "/content/gdrive/MyDrive/DataSets/house_price_data/"

(7) Download the dataset.

!kaggle competitions download -c house-prices-advanced-regression-techniques

Answer: Most important part is before to download files:
In the Kaggle webpage, in the Competition section you must clicked on:
Late Submission or on Join Competition
and
ACCEPT RULE AND CONDITIONS ON KAGGLE COMPETITION WEBPAGE
if not, after copying api file, and after launched downloading the dataset, 403 error shows as result.
Answer: A hacky way:

Go to the dataset page after login
Open Chrome Developer Tools, then go to Network pane
Click Download button on Kaggle
When clicked you will see many requests in Network pane, find the request starting archive.zip
Right click on that request, then Copy -> Copy as cURL (bash). Now you copied the command
On Colab, paste the command and append an ! to the beginnning of the command then run it

This is definitely a less reliable way than the API, but still remains as an option.
Answer: I find the accepted answer to be very comprehensive, but would like to add that:
!kaggle competitions download -c dogs-vs-cats

or most other downloads still wont work. You will probably get the following error:

403 - Forbidden

which is not very verbose. It wants to say: "Please visit kaggle.com and accept the rules (e.g. for that competition). You cannot accept through the API! It is explicitly stated in the docs (see Public API documentation | Kaggle):

Just like participating in a Competition normally through the user interface, you must read and accept the rules in order to download data or make submissions. You cannot accept Competition rules via the API. You must do this by visiting the Kaggle website and accepting the rules there.

Yes, this could have been a comment, but I am missing enough reputation to comment.
Answer:
import os
os.makedirs("/content/.kaggle/")

import json
token = {"username":"your_username_here","key":"your_kaggle_key_here"}
with open('/content/.kaggle/kaggle.json', 'a+') as file:
    json.dump(token, file)

import shutil
os.makedirs("/.kaggle/")
src="/content/.kaggle/kaggle.json"
des="/.kaggle/kaggle.json"
shutil.copy(src,des)

os.makedirs("/root/.kaggle/")
!cp /content/.kaggle/kaggle.json ~/.kaggle/kaggle.json

!kaggle config set -n path -v /content

#https://towardsdatascience.com/setting-up-kaggle-in-google-colab-ebb281b61463

!kaggle datasets download -d xhlulu/siim-covid19-resized-to-512px-png

Works for me on Colab as of 29-05-21!

Using Kaggle Datasets in Google Colab


After removing linux Grub error

Question: I have a dual boot Windows & Linux system. I removed the Linux partition, but after that I am not able to go in to Windows XP. It is not booting. It gives me a GRUB error.
Comment: Possibly related: [How can I uninstall Linux from a dual-boot machine?](http://superuser.com/questions/521381) over on SuperUser.
Comment: You've removed Linux but kept its bootloader... You need to switch to a Windows bootloader.
Answer: You just need to repair your MBR.

Go to XP's recovery console using a bootable CD/pendrive.
Navigate to your OS drive. For instance E:
Run fixmbr and reboot.

This will remove GRUB and install the Windows MBR.
Answer: I'm not sure I follow, but what do you want to do? If you want to completely remove Linux (sadly), you're on the right path. You just have to boot into your XP CD and let the Windows setup take care of repartitioning and installation. Why do you need Grub?
If you want to use both, Grub is obviously not able to find the Linux kernel that you deleted. The easiest way is to set up your partitions with something like Gparted, reinstall XP first,  and THEN your Linux distro (with Grub)from an iso or network.
Comment: You misunderstood me, The problem he faces is that there is no bootloader (Grub starts, but cannot find its files), but to get the windows bootloader in place of grub's, he does not need to reinstall windows, he just needs to reinstall windows xp bootloader over grub.
Comment: He should not reinstall windows, he probably only needs to do boot recovery to reinstall windows xp's bootloader.
Comment: Yes, he can reinstall from the Grub command line, but I don't see the point if he just wants to use Windows without another OS. Excuse me, I understood that he had deleted the partition on purpose.
Comment: The XP bootloader can be installed without the rest of Windows?
Comment: I didn't realize that was even possible on Windows.. Sorry.
Comment: http://www.neowin.net/forum/topic/292614-how-to-get-back-your-windows-xp-bootloader/
Answer: 1.Enter in System Setup by pressing F2.
2.Select "File Browsrr Del Boot Option" &press Enter.
It will Show list of all partitions on hard Disk
3.Select Linux Partition You want to Delete & Hit Enter
4.Now save all  Settings by pressing F10.
Now your PC  will restart and Windows  will start normally.

After removing linux Grub error


zip password cracking with permutation

Question: I have a zip file (.zip created by 7zip v15.10) that I remember the password to (~12 characters long), but it seems I've typed the password wrong while zipping it and now it doesn't open.
What are the best tools to recover the password based on the permutations of what the password should have been?
Some paid zip cracker software claim that they're able to find the right password based on what the password should've be by trying the permutations of it, what I want to find out is: are their claims true?
A year ago I've tried the trial version of one, it had one method that I would start typing the password and at some point it told me that "password found" but to see the password I had to pay for the full version first. I couldn't verify that their claim was true and since their last update was 5-7 years in the past, I was hesitant paying to find out.
Comment: please edit your question and provide the following information:  the format of the file, including the version of the software used to generate it, and the possible range and number of characters in your password (the worst-case scenario)
Comment: It's certainly possible that "some paid zip cracker" might be able to use some clever tricks (e.g., as you type it tries the letters you type and typical typo letters close by on the keyboard--like if you type "k" it tries "k" "j" "l" "i" "m" ","), but it is a little hard to give a good answer if we don't know the specific "zip cracker" and the specific claims.
Comment: See https://security.stackexchange.com/questions/240072/are-files-encrypted-with-7zip-vulnerable-to-password-crackers
Answer: The tool you need is called HashCat.
In the first instance, you need to specify or extract the stored+salted hash that is within the zip file, eg:

hashcat -m 13600 "your_zip_file.zip" ^ (for 7z zip files)
7z2hashcat (for 7z files)

(^ See this discussion on various zip formats in hashcat: https://forum.hackthebox.eu/discussion/3783/zip-password-crack)
Then, you need to configure hashcat to limit the range of characters from which it will draw its possible combinations. This is addressed in the documentation.
edit: to clarify: you don't specify the total number of possible characters in your question, so it's not possible to predict or speculate on possible hashcat configurations, however, the tool allows you to specify the charset that applies for a particular placeholder, viz. https://hashcat.net/wiki/doku.php?id=mask_attack#examples - in your case I would recommend creating more than one (max four) custom charset with the possible known characters at various regions in your password - the more constraints you can impose, the less the total number of tests that must be executed.
Depending on how many possible combinations there are, you may wish to parallelise the operation. This is beyond the scope of this answer, however, here's an idea about how to approach the problem: Hashcat performance on AWS EC2 GPU instances de Koning 2019
Let us know how you go ... good luck!
Comment: Sounds like brute force cracking with limited characters. Some paid zip cracker software claim that they're able to find the right password based on what the password should've be by  trying the permutations of it, what I want to find out is: are their claims true?
Comment: @KiaAzad What exactly do you consider a permutation? To me that just sounds like they're trying slight variations on your guess which is basically equivalent to a brute force attack with a narrowed search space.
Comment: @tln05 well, I mean exactly what you've described.
A simple brute force attack checks all combinations, but a more sophisticated algorithm might be able to skip some and try the ones that have a higher chance to be the right password first based on the user input.

zip password cracking with permutation


Scaling Up an Elasticache Instance?

Question: I'm currently running a site which uses Redis through Elasticache. We want to move to a larger instance with more RAM since we're getting to around 70% full on our current instance type.
Is there a way to scale up an Elasticache instance in the same way a RDS instance can be scaled?
Alternative, I wanted to create a replica group and add a bigger instance to it. Then, once it's replicated and running, promote the new instance to be the master. This doesn't seem possible through the AWS console as the replicas are created with the same instance type as the primary node.
Am I missing something or is it simply a use case which can't be achieved. I understand that I can start a bigger instance and manually deal with replication then move the web servers over to use the new server but this would require some downtime due to DNS migration, etc.
Thanks!,
Alan
Answer: Elasticache feels more like a cache solution in the memcached sense of the word, meaning that to scale up, you would indeed fire up a new cluster and switch your application over to it. Performance will degrade for a moment because the cache would have to be rebuilt, but nothing more.
For many people (I suspect you included), however, Redis is more of a NoSQL database solution in which data loss is unacceptable. Amazon offers the read replicas as a "solution" to that problem, but it's still a bit iffy. Of course, it offers replication to reduce the risk of data loss, but it's still nowhere near as production-safe (or mature) as RDS for a Redis database (as opposed to a cache, for which it's quite perfect), which offers backup and restore procedures, as well as well-structured change management to support scaling up. To my knowledge, ElastiCache does not support changing the instance type for a running cluster. This suggests that it's merely an in-memory solution that would lose all its data on reboot.
I'd go as far as saying that if data loss concerns you, you should look at a self-rolled Redis solution instead of simply using ElastiCache. Not only is it marginally cheaper to run, it would enable you to change the instance type like you would on any other EC2 instance (after stopping it, of course). It would also enable you to use RDB or AOF persistence.
Comment: Thanks! You're correct that we're using Redis as a quasi-database solution, we're actually planning on having 2 redis servers running, one which acts like a traditional cache in front of our database. It's the second server which the data needs to be kept across up-scaling which we're concerned about.

We're now looking at using Scalr.com to manage our Redis servers as they offer read replicas and what appears so far to be very fast failover. The advantage is that we can scale up  to what ever AWS instance type we want.

Thanks!,
Alan
Comment: To address the last point made, ElastiCache Redis does allow RDB snapshots and AOF: "The Redis slave can be used to generate RDB snapshots and / or AOF append logs as needed, and you may transfer these files to S3 for durability." From https://aws.amazon.com/elasticache/faqs/#redis-features
Comment: Yes, of course, I might have taken it a step too far. Scaling up by tearing down the instance and building another based on a snapshot would of course have solved the immediate problem here. However, I do stand by what I said: I would not recommend using ElastiCache as a database. And I doubt Amazon itself would either.
Answer: You can now scale up to a larger node type while ElastiCache preserves:
https://aws.amazon.com/blogs/aws/elasticache-for-redis-update-upgrade-engines-and-scale-up/
Comment: Whilst this may theoretically answer the question, [it would be preferable](//meta.stackoverflow.com/q/8259) to include the essential parts of the answer here, and provide the link for reference.
Comment: Worth noting that this works only for Redis clusters but not for memcached.
Answer: Yes, you can instantly scale up a running Elasticache instance type to a larger size. I've tested it and experienced very little actual downtime (I think a few seconds at first, but very quickly it's back online, even while the Console will show the process taking roughly a few minutes to actually finish.) I went from a t2.micro to a m3.medium with no problem.
Answer: You can scale up or down

Go to Elasticache service
Select the cluster
From Actions menu in top, choose Modify
Modify Node Type as shown below

If you have a cluster, you can add more shards, decrease number of shards, rebalance slot distributions, or add more read replicas. just click on the cluster itself, you should be see something like this

Be aware when you delete shards, it will automatically redistribute data to other existing shards so it will affect on traffic and overloading other shards, when you try to delete a shard you would get a warning like this

Still need more help, please feel free to leave a comment and I would be more than happy to help.

Scaling Up an Elasticache Instance?


Send selected token (the one you deployed) with web3js

Question: How to send a transaction of a token that I have in my wallet other than the default one like ether in Ethereum without a contract method just with web3js?
Answer: To interact with a contract on a blockchain, you must have to communicate with a RPC or any other endpoint prefer. To that you may have to use a direct API call, a library like web3 or ethers from a script, a web interface like a blockscan website (etherscan, bscscan, etc...) provide or a wallet application.
However you have to call the contract method transfer or transferFrom directly or indirectly.


can not update fresh installed( SharePoint enterprise 2013 with SP1) farm with july-2020CU

Question: I've sharepoint 2013  farm with SP1 installed in win server R2 and there was error during sharepoint installation and  I edit 'Iglobal \ oserver.msi' with orca and it goes right and installed after that I try to install any update from april 2018 CU to Aug 2020 still gives me this error 'The expected version of the product was not found on the system '
Answer: You should start over. If you're having to edit an MSI for the installation, something went wrong.
Comment: I read  a lot of errors about installing sharepoint with sp1 on win server 2012 R2 ,should I use win 2012 instead
Comment: No, but in order to install 2012 R2 you need to use the SharePoint 2013 *with* SP1 ISO. You also need the 2012 R2 media handy for the .NET Framework install.


Why do we need frequency of changing current for induced EMF?

Question: I know that a constant current doesn't create induced emf, however, I do not know why a changing one does. Are there any ways to understand it briefly/easily, or is it just the way it is?
Comment: Physics doesn't ever really answer "why" things are. It mostly tries to describe what we observe in the universe around us. In this case, we observe a back-emf when we try to change the current through a loop, and we can describe the effect with Faraday's Law.
Comment: Okay, thank you! I do not want to be like memorizing equations without understanding what's really happening, but I guess I can do it without knowing the why for most cases.
Answer: You can understand this through the Faraday Law:
$$ \varepsilon = - \frac{\Delta \Phi_B}{\Delta t}$$
Here $\varepsilon$ is the EMF, $\Phi_B$ is the magnetic flux which equals the multiplication of a magnetic field $\bf B$ and the area $\bf A$ crossed by $\bf B$, whereas $t$ is time, and $\Delta$ represents changes. So the equation just says that the EMF can be produced by the magnetic flux that changes over time.
Furthermore, in the special case you mentioned $\bf B$ is produced by the electric current. So assuming there's no change in $\bf A$, the only way to produce $\varepsilon$, i.e. the EMF, is by having $\bf B$ that's changing over time, and in order to get $\bf B$ that's changing over time you need an electric current that's changing over time too. So that's how it's explained!


How to start?? From where to start?

Question: I want to know how should I start my journey
I'm trying to start my spiritual journey but all the time something comes in the way
2 months ago I started doing ajapa japa after 21 days I got high fever after getting well I started again then my family planned a trip to kolkata without telling me so I failed again
I've been following celibacy from 4 months but today I saw video of girl normally I have that much control on myself but I don't know what got into to that I opened porn site thankfully I didn't masturbate every time I started foing something spiritual something comes in the way its like something dragging me down
Some scripture say find a guru how tf am I supposed to find a guru I visited some big temple of kolkata like dakshineshwar,kaighat,blur math(place where ramkrishna paramhansa initiated vivekananda) in hope to find a guru or someone who can guide me I spend as much time as possible there but nothing
4 months ago I broke contact from all of my friends so that I can meditate as much as possible so I lost all of my frnd
Now I'm fked both sides
Comment: Also, if we're starting on this path now, we're gonna be on it hopefully for years & decades right ? Assuming we don't get hit by bus hahaha :P So yeah anyway, maybe think of it more like a slow burn kinda thing, rather than starting too much then it's very enormous & formidable and we couldn't get anywhere. You know how they say w/ huge stuffs, break into little pieces, make lists, and go one thing at a time. It's ridiculous that I know less than everyone here but seem to be writing out such huge advice, um ok ! :) Anyway maybe one of the more knowledgeable types will put a reply below too :D
Comment: @Miss I'm surely going to start again there's no doubt about it and I have no problem in following it for yrs but even time I start something happens also I don't stopped contacting my friends on purpose, after doing my classes I got so little time which I choose to spend in meditation and other stuffs
Comment: @Abhinav Raj  What exactly do you want to focus on first??Do you want to get started with meditation/brahmacharya/learn more abt a specific philosophy? As its really hard to try to learn everything at the same time due to your time-crunch. **So Kindly please edit your Qn and ask more specific Qns**
Comment: Your Question is too broad.Please edit your question and ask them one-by-one.This seems more like a rant than a question.Sure here people are there who would help you but if could kindly be more specific, we could help you even better.Kindly also search your question before asking a new question, chances are some of them might already have been answered in the past....
Comment: Maybe go lil more gradually, slowly with it ? I started following Shakta path earlier this year for first time in my life, so am pretty much brand new to this also. I understand feeling kinda uncertain how to proceed. Maybe just go lil more slowly with things ? Even if stuffs got messed up by Kolkata trip, just try and resume again bit by bit ? If gets interrupted again, no big thing, resume after that too. And just my personal opinion here but I def don't think you gotta eighty-six your friends and relationships for this. I'm on Shakta/Tantra path & it never says anywhere that is necessary.
Comment: Maya does cause troubles when one heads spiritually....
Comment: @Rāmachandra well I think I'm not as knowledgeable as you are I did read some scriptures related to yoga like hath yoga and gheranda samhita after that I came to know about meditative techniques like ajapa japa(focusing on sound of breathe) so I started doing it I started with 64 times (3 sitting in a day) as mentioned in gheranda samhita then increase it 5 times everyday I'm not initiated yet so I don't want to get into any type of tantra/mantra sadhna I'm simplifying my question for you every time I start meditation after some days something happens that broke my rythm so what shall I do
Comment: Stop practising advanced meditation techniques like Ajapa japa in the absence of a Guru. Hatha Yog is very practical, it requires carefully guided practise under the watchful eye of the Guru.Wrong practise can lead to all sorts of body ailments as it leads to imbalance of major vayus in the body. Meditation is usually combined with asanas which ready the body to be fit for meditation(Acc to Hath yog pradipika many steps of Ashtang yog are to be done prior to starting meditation which i havent mentioned here).
Answer: Another point of view thru Shri Ramsukhdas Swami
Shri Ramsukhdas Swami , is a contemporary ascetic (of Rajasthan 1904, lived 102 years), since his young age of 4, who travelled across India with a prime objective, to spread the message of Bhagavad Gita.He was absolutely devoid of any ostentation.(stayed away .. from being photographed, getting his feet touched, making disciples, accepting gifts , donations, accumulating money or things etc., building ashrams (monasteries), making cults etc.)
His works are published by Gita Press
Gorakhpur.
His  book (cited below)  is sure to answer the question posed here , as well as , could clarify several related doubts ( in  the light of scriptures)
Is Salvation not possible without a Guru. Published by Gita Press. Gorakh pur.
(Quoting a portion from Sri Ramsukhdas Swami s book)

Q :  How can salvation be attained without a Guru because it is
mentioned in Ramacharitamanas that no one can cross the worldly ocean
without a Guru? "Guru binu bhav nidhi tarayi na koyi" (Manas, Utter. 93/3)
Ans  It also means that salvation is not possible with the help of a fraud Guru. Only having a Guru is not sufficient. Salvation is only possible when you follow the path shown by a real saint and in that case he is your Guru. When anybody's teachings help us to attain salvation, he becomes our Guru even without declaring so. On the contrary if we have a Guru but we do not follow his teachings, it will not lead us to salvation.

Q :  How can a person who can differentiate between good and evil be
called one without a Guru?  Ans  Everyone possesses the discretionary knowledge
(vivek) to judge good and bad. He also knows to repeat the Name of the
Lord, to remember God and to not harm anybody. The source of all this
knowledge is a Guru.It is not necessary that one can attain salvation simply by having a Guru, but one can attain it by one's own yearning and strong desire for it.God is the Guru of the whole world " Krishnam Vande Jagatgurum You are also a part of this world, then how can you be without a Guru? Therefore
stay in company of noble saints and follow their teachings.

You are not capable of testing or cross-examining a Guru. If you
were able to test a Guru, then you have become the Guru of the Guru. Can
one who can test a Guru be any thing less than the Guru? The one who can
examine a Guru, is great. In such a state, it is best that you not make
anyone a Guru and simply engage in spiritual discourses and self-study, and
whatever talks appear to be appealing, imbibe them in your life. Have
association of such saints in whose company, your intensity for God
Realization increases, bad conduct and bad qualities naturally go away on
their own, and good qualities and good conduct come on their own, when
God is remembered in a special way, when faith and trust in God increases,
without even asking questions, the doubts are resolved on their own and the spiritual guide desires to take nothing from us. Benefit from them without engaging in a Guru-Disciple relationship. If you see any faults in him, or something appears to not be right, then leave that place.

The scriptures recommend leaving such a Guru -
Gurorpyavaliptasya kaaryaakaaryamajaanatah |
Utpathpratipannasya oarityaago vidheeyate ||
(Mahabharat, Udhyog. 178/48)
"If a Guru, out of his false ego, forgets what to do and what not to do and
proceeds on a wrong path, he should be given up, it is sanctioned by the
scriptures."
Gyaanaheeno guroostyaajyo mithyaavaadee vikalpakah |
Swavishraanti na jaanaati parashaanti karoti kim ||
(Sidhsidhaantsangrah, Gurugeeta)
"An ignorant, untruthful and confusing Guru should be given up, because the
one who could not attain tranquility and peace himself, how can he give peace
to others?"

Q. :  It is believed that when a Guru gives a secret teaching (Guru
Mantra), it becomes more effective, is it true?
Ans:  Such a secret teaching or Guru Mantra shall be effective only when
the Guru (teacher) himself is effective. One who does not possess any
effective power, how can he impart effective power through his secret mantra?
Therefore it is said -

Vachan aagale sant ka, hariyaa hasti dant |
Taakh na tute bharam ka, saindhe hi binu sant ||
It means that utterances of a realized saint are as powerful as the teeth of an
elephant, which break open the doors of ignorance. An elephant can break
the doors of a fort with his teeth, but without the elephant, and merely with
his teeth alone, one cannot break the doors even if they so desire. The
reason being that the actual strength is in the elephant, and not only in his teeth. Similarly, effective influence lies in the life experiences and
impressions (anubhav) of the saint and not in his hollow utterances alone.

Q. : Some people get super natural experience from awakening of
Kundalini with the help of some Gurus. What is this?
Ans :  Such miracles do happen but they do not help in attainment of
eternal bliss or salvation. Salvation takes place when one transcends the
body and the world.
Answer: Well the answer maybe, completely just from my point of view. And maybe long as well.
Well,I would say every spiritual person goes through such a phase where one is between running behind spiritualism and Bhogas and thus in a chains of delimeas, if you experienced this you are on right track. These questions flung straight upon everyone's face, that from where do I start, how do I do etc. These are the sign boards that shows, your in the right swamp. But, people online can pour their thoughts and answers but you need to find your story and waking point.
How should I start my spiritual journey!
That's a queetion that doesn't count if your dedicated. Okay so let's go from some basics, right! I too am a zero level and neo Bhakta, but I can  say there is no benchmark that reads here starts the spiritual life(until some incidents change your life, like mine did). Why so? Since, you don't need any specialization or course to be Astik and a Bhakta, or say embark the journey. Because, Adhyatma is very much core of life. Other activities are surrounded around it and not vice versa. But, yes your turning point can be towards the ishtadevta. See the fact that you want to meditate is praiseworthy enough. But, kindly save it for a little late. Because, first kindly calculate who is truly your isht devi/devta amongst the Panchdevtas (Surya, Shakti, Shiva, Ganesh, Vihsnu).                        Why the need for ishta? Because u need some focal point to start. For someone it might be say Krishna, Shiva, Paramba etc or any particular deity. It is because we can dedicate ourselves to them.
Like Say you meditated, but upon what? Initially you need an object to meditate upon (Im not talking about trataka or any vigraha, I mean a form to begin with) because, we are not so advanced sadhakas, that we can meditate on formless Brahma at such a juvenile stage.
So, once you have chossen your ihsta devta, next thing is to surrender onto him. Surrender all your tendencies to the deity. Lust, love, anger, jealously everything to the deity. Say if you love someone, your all tendencies will be to make that person happy. So, that object is our diety. This is called doing Sampurna Sharnagati. Your eating, your walking, your sleeping, your each and every action is then dedicated as if to that deity. Then, even if you are in the world, you won't feel the burdern that Im not spiritual or I need to strech an extra hour for my puja as slowly your mind and tendencies start to dissolve into the deities Roop, Saundarya, Dhyaan Bhajan etc.
Because, if you think all your actions are for Bhagwati, nothing can bother you, srry to say even if someone plays porn next to you, you wouldn't even think of the thing going around you. (These are not my words but the words of the acharyas that I learnt, honestly I'm no Indrajeet person who have right to preach since I too am drawn by senses. But, that's how things happen over time.)
' I visited some big temple of kolkata like dakshineshwar,kaighat,blur math(place where ramkrishna paramhansa initiated vivekananda) in hope to find a guru or someone who can guide me I spend as much time as possible there but nothing.'
Indeed how can we find guru out of the thin air? Because to find a guru means to go after a deity, an Achar, a Parampara, A sampradaya, be it Natha yogis, Vaishnavas, Kaulas, Vamacharis, Shaivas, Smartas or any other sampradaya. Untill we are loyal to one, how can we find a guru.
So, firstly calculate the ishta devta, the sampradaya or achara that appeases you. Then just simply surrender to the deity and ask for guidance and trust me paths will open automatically for you. For now read Purans, great works from the realized souls like RamaKrishna Paramhamso, do Vani path or stotras, something that have connection to your deity whenever you get time. Since, at initial stage when a person tries to step in adhyatma is very cloudy, and balancing daily life and getting spiritually progress is hard enough.
' 4 months ago I broke contact from all of my friends so that I can meditate as much as possible so I lost all of my frnd Now I'm fked both sides. '
As I said, such things do happen. It was all divine play. So, better no lament because you actually lost nothing neither it's late.
Start with the basic steps like start reading shastras, do naam jaap and Stotra path, listen to some acharyas (not self proclaimed ones) Shree Hit Premanandji Maharaj, Rajendradasji Maharaj, Shrungeri Jagadguru Shankaracharya, Raghvacharyaji (these are the best and true Dharmatmas on YouTube I know till now.) Since, daily stasang is needed. I would say get into the HSE chat box here, as many leaned scholars are here with bigger brains and heart to guide you, no doubt.
It is never to late anyday, hurdles comes for us, because a single step into Adhyatma is one by one step out of life and birth cycle.
I have something which is my favourite line from the Shakta Shastra to boost your morale,

चंडीका उवाच,
यश्च माम् भजेत नित्यमं वित्तम् तस्य हराम्याहं |
करोमी बंधुविच्छेदम् स तु कष्टेन जीवती ||
एषु तापेषु संतपह् यदि माम न परीत्यजेत |
दियते परमस्थानं यत् स्थानं विष्णु दुर्लभं ||
Chandika devi said,
Those who are devoted to me, I take away all their wealth. I make him loose all his friends and torture him alot. Even after this, if a person, if he doesn't abandons me despite all those odds and keeps worshiping me, I free him from all miseries and give him that place (here it means parampada) which is even difficult for Vishnu to get.

This verse is not to scare anyone, but it shows that stepping into adhyatma is not a cakewalk. Only with steadpointed focus and determination one can reach the isht devta. So, buckle up your shoes and get into it.
Edit- Sorry I was unable to add the comments and also was also unable to write more in chat box due to limit. So, I will add here.
See everyone here is either working or studing. No one have free hours like 6-7 hours to sit in front of the deity and do bhajan kirtan and get anugraha, because you can say we are into samsara for say grihasta dharma. So, daily wordly transactions are needed to be done and followed. But how? Those actions must not be for ourselves. Take an example, you wish to today eat say Roshagulla, now that is bhautik iccha in us, which one must refrain from, since eating for the sake of tongue is considered a sin in all shastras. So, how do you do that? The best option is buy the Roshagulla and first do naivedya to the deity. So, simply do that for the priti for deity(to make her happy) and take that Roshagulla as prasad. Likewise say, we are studying, but here the motto must be to study for the sake that if we study hard enough, we can realize our dreams and have enough money to do nirvaha of our Grihasta Dharma in future and do Daan, Dakshina, yajna and nitya and naimittik pujas for Kuldevtas, Rishis and Pitras, etc. That's how we surrender all our daily life activities to the deity. For example if you cook something to eat for yourself, (alas since we have to fill our stomach) so you must have the bhaav that, Im cooking for my Deity. First I will offer it to her/him and then partake it as Prasad. Say you are sleeping, the bhaav must be Im sleeping now so that I can awake up in morning and worship my deity again. If one is bathing, the bhaav must be we are bathing so that we can cleanse the body and engange ourselves in Dharma. Thats how you do it, even if you have no time, yet you are doing all daily activities for deity and thus doing a upasana in itself. And that's how most Dharmik Grihastas be like.
See the basic problem of lust, anger, jealousy is in me too. But then there we must use our viveka. Whenever we find ourselves helpless and surrounded by say lust, we must cry to the deity to help us to overcome the tendecy and hormonal stuff. It's hard, even I fail at times to subdue the urges then comes in starting to do jaap of the devta loudly, turn on their bhajans. Slowly the tendency would be gone. For anger issues, it's spontaneous, we can't help. All we can do is first ask for sorry from that person and make a resolution that we wil be maun(silent) even if anyone dares to poke us. Anger issues are truly a problem but, by remaining silent, you done the 50% job, because if you don't speak anything things would get into places ontheir own.
The next problem I forgot to address earlier was, you said you tried to do Ajapa Japa. See, what is Ajapa Japa? It is when your body doesn't even knows (isn't even conscious that japa is happening) and your mind is constantly thinking of the deity and doing japa that's Ajapa japa. Okay, so say we couldn't even practice the meditation for few days, how can we do Ajapa japa which is the higgest stage of japa? It's like a 10th std kid saying I entered IITs. That's not possible. Because even that kid went to IITs and attended the lectures, it's wastage of time! Because, he won't be able to grab anything, since he have wobbling basics. And finally he would be demotivated and give up studies saying I worked so hard but failed. It's because we skipped the basics and hoped to advanced level. Same applies here. So, as I tried to put my thoughts, kindly select an ishta devta (there can't be 2*3 deities at a single time whom you consider as isht) and start doing their naam jaap (chant their name, for eg, Durga Durg Durga, or Shiv Shiv Shiv). First to Vacik japa (with mouth) then slowly over years you won't even know and your Ajapa Japa would be started.
Hope I made sense in here and this helped you. In case if you have more queries, you can ping me on telegram. I have the same username there as well.
कालिकार्पणमस्तु |
Comment: Best answer❤ Also can u pls explain total surrender part
Comment: I mean how am I supposed to surrender all my tendencies to my deity I am an engineering student so I have to spend 7-8 hours in studying so how am I supposed to dedicate my studying,my eating and my everything to my deity also I have huge problem dealing with lust and anger so how am I supposed to dedicate these type of things to my deity
Answer: Let me tell you an example from a text where Shiva taught how to approach something we are unaware of.

First identify best possible method of doing a thing available across the globe.
Then identify the 2nd best possible way or the middle/average path.
Then the lowest possible and so on.

Now try to approach the first one according to your life condition/health/ashrama etc.
If you think you cannot do it or not have the required capability fallback to lower one and so on.
This approach needs some home work and consultation. You have to follow your gut feeling.
If you don't find any guru take help from Shastras, even if you fail in this birth and you have the genuine desire, your desire for spiritual upliftment will follow you in next birth.
Start with Bhagavada Gita, it contains the cream of all the shastras.
After you can understand it you can choose your direction based on your taste and attraction towards Hatha Yoga, Tantra Yoga or Bhakti Yoga etc.
This approach is taught by Shiva in context with the spiritual aspect and mentioned in some Kashmiri Tantric text which i am currently not able to recall, i will add the exact quote as soon as find the source.

How to start?? From where to start?


Static IP affecting my Network

Question: I have a small network i use to redistribute internet. Now from what i kniw , routers usually map a network depending on which port its connected to. They work at Layer 3. We have been having an issue whereby we found most of our packets were being dropped...we solved it, it was a faulty switch, Long story short. A colleague has tried suggesting that someone using a software i.e connectify ,was using our gateway address 10.0.0.1 as a static ip therefore creating chaos. We saw the ip logged in the hotspot software we use. Now i dont think this is possible. But can that confuse a switch. if it stores two Mac addresses that point to the same place?
Answer: It is not possible for a switch to have a MAC address assigned to more than 1 port. When a MAC address is seen on a new port the switch simply updates its records to show the MAC is on the new port, overriding the old entry. Loops can cause the switch to do this at an excessive rate and is called a mac address flap. Usually switches will log mac address flaps to the buffer/console.
If I understand you correctly then you are saying that your default gateway address is 10.0.0.1 and someone else also assigned their computer 10.0.0.1. That wouldn't confuse a switch as a switch doesn't care what IP you have, a switch works at layer 2 and deals exclusively with MAC addresses. What is more likely is that due to the duplicate IP address, some of your clients were ARPing for 10.0.0.1 and receiving the real routers MAC address and some were receiving the 10.0.0.1 clone MAC address and sending traffic there instead of the router. Any traffic going to the clone would have been dropped. Any traffic going to the router would have been forwarded (assuming its configured correctly). This could give the impression that the switch or router is dropping packets but in reality the switch is just forwarding the traffic to the destination MAC address that the clients requested.
Comment: Thank You. So now, This means that nevertheless some packets are getting lost when they are fowarded to the clone gateway? This mean that someone can just mess up my network by using a static IP? since some clients will be getting inconvineinced when the packets are fowarded to the clone? what to do then? How would you advice i stop this guy? MAC Address filtering?
Comment: Use dynamic arp inspection. Its designed to prevent this exact scenario. What you may not realise is that by pretending to the gateway any traffic sent to the clone can be captured and inspected. Any unsecured traffic containing sensitive info can be read by the "man in the middle." Note that to use DAI, you may need to turn on DHCP snooping. These are features on most managed switches.

Static IP affecting my Network


Can you break out of jail and not get attacked?

Question: If I go to jail and manage to get my stuff and break out without the guards seeing me, will the guards outside of the jail attempt to attack/arrest me again, or will they just leave alone for a while and say that famous, "Wait, I know you!" (xd)
Comment: I am not too sure about being attacked as I am more of the stealthy type than mass murdering sorts when doing crimes but they will definitely attempt to arrest since the bounty is not cleared. Usually at the instance when I first escape from a jail they will only arrest if they see me or I talk to them.
Answer: If you escape from jail, your bounty will remain, plus you risk an additional 100 gold bounty if you're caught while trying to get out.
Answer: When you perform a jailbreak a bounty of 100 gold is added to your current bounty - this happens regardless of getting caught. After completing the jailbreak guards will not interrogate or attack you, only saying "Wait, I know you!".
There was conflicting information about this online so I tested it without Mods on a fresh character. I stole a knife in Riverwood (9 gold bounty), ran to Whiterun and talked to a guard, got sent to prison, escaped, grabbed items on way out, ran around town jumping in front of guards with 109 gold bounty.
To remove the bounty you'll need to pay it. Or,

 If you are part of the thieves guild and have enough reputation in the specific hold there will be a bribe a guard option to pay the bounty at a discount. If you use this bounty payment option you can immediately steal back the bounty from the guard (so I've read online).

There's also wikia guide on how to escape each of the jails.


Do I have to generate a rigify rig to make animations for a game?

Question: I'm pretty new to rigging with rigify but the rigs that rigify generates are consistently a hassle compared to just using the metarig bones to animate. I'm using the 3d model for a game in unity, is it possible to just animate using the bones while never generating a rig?
Answer: If animating using a rigify-generated rig is "a hassle", animating using the rigify meta-rig will be a bigger one, so I recommend that you learn how to effectively use the generated rig.
That said, yes, you can use the meatarig.  Simply parent the original mesh to the metarig the same way you would parent the mesh to generated rig; don't create a generated rig; and do your animation with the metarig in pose mode.
Comment: Thanks for the answer, although in what way is using the meta rig to animate a hassle?
Comment: There is no support for inverse kinematics, a technique that often makes positioning limbs much easier.  Several features that reduce the need for compensating for movement in one part of the rig so that another part doesn't move when it's not supposed to are missing, resulting in the animator having to counter-animate things like head position when the torso bends.   You'll spend a lot of time counter-animating and bone-by-bone positioning if you use the metarig.
Comment: I'm personally fine with those drawbacks, auto IK counteracts the lack of inverse kinematics and counter animating doesn't matter that much since they're pretty simple skeletons. Thanks for the response though.
Comment: @a1998ToyotaCorolla best of luck.  Since you're apparently a new user to Blender StackExchange, you might want to read [What should I do when someone answers my question?](https://stackoverflow.com/help/someone-answers) and perhaps upvote or accept my answer
Comment: Yeah, I'll do that. I tried upvoting earlier but it said "you need at least 15 reputation to cast a vote"


First name or last name(s) in a biography?

Question: I'm deep into a biography of a well-known person.  He was born with a last name, took his mother's last name following her divorce, took his stepfather's last name following her remarriage, then took a stage name by which he became famous.  The only consistent name was his first name, and I've stuck with that throughout the book.  But it worries me that it seems too familiar (I never knew him personally).  At the same time, it provides, as I say, consistency and avoids confusion between him and his father's and stepfather's last names.  I've considered using his first name for his boyhood, then switching to his adoptive last name as he becomes a man, then switching to his stage last name once he takes that on.  But I fear that might be confusing.  I'm interested in informed thoughts on this particular situation.
Answer: I assume the book will be marketed as a biography of the famous actor and will likely have that name in the title or subtitle, and certainly in the blurb. And that will be the name for which your target audience will pick up the book.
I would therefore use that name as the main or reference name in the book, to which you fall back whenever you want to make sure everyone understands who you are talking about.
I looked at some recent biographies, and most try for a close third person narrative perspective that gives an impression of allowing the reader a glimpse into the mind of the protagonist. The narratives often switch between using the last name when the narration is more distanced, for example in the introductory sentences of each chapter or passage, where we hear the narrator telling us where we are in time and in the history of the person, thus providing orientation, to using the first name when we are getting closer to the portrayed person and his or her emotions, motivations and experiences.
In the biography of Elon Musk, for example, we have something like: Section 1: Elon Musk, Elon, Elon, Elon, Section 2: Musk, Elon, Elon, Elon, etc.
How you deal with a person changing their name, will depend on that person's relation to their name(s):

Switching the name in the narrative along with the name change. I would do this, if the person changed their name in an act of becoming that person. That is, if the name change is an aspect of the identity of the person, as in marriage or adoption.
Example:

Mary Brown was born as Mary Greene in 1964. At first, Greene lived in Boston with her parents. Mary went to school etc. In 1987 she married Robert Brown. Robert was nice to Mary. Mary Brown became a mother. Mary loved her children. Brown [that is, Mary Brown] later became a politician. Brown was the first female president of the United States. Mary always remained a loving mother. Brown died in 2014 of a heart attack.

Here Mary Greene becomes Mary Brown, so the narrative executes the name change with her.

Stick with the name under which the person is known. I would do this, if the phases with different names are looked at from the perspective of the person with the main name, for example if the person never really identified with that name (e.g. a derogatory nickname or the fake name of a fraudster) or the narrative perspective is strongly rooted in the present day and the past is always interpreted in relation to who the person became later.
Example:

Nick Knight took on the name of Nicholas de Grenville to relieve rich ladies of their money. "Baron de Grenville", Mrs. Bell addressed him. Nick looked at her and smiled his most slimy smile [close third person]. Knight had always been a natural with women and employed his skill yet again [interpretation by the narrator].

In this example, Nick Knight isn't really Nicholas de Grenville, so as a narrator I wouldn't use that name (except if I wanted to mislead the readers as to the true identity of de Grenville, for example in a detective novel).
Example:

Bono was born Paul David Hewson. As a child, Bono learned to sing and thus laid the foundation for his later career. Bono loved his mother, when he was a teenager. "Paul," she used to say, "I love you." Bono admired her as a younger man, and still does to this day. In an interview in 2023, Bono said that he didn't like school. [I made all that up.]

Note how in the second narrative all the past events are put in relation to the Bono that we know.
Comment: Please don't use code formatting for quotes. (If I were to use my screen reader on it, I would be hearing the punctuation instead of it being read like regular text.)
Comment: @Laurel Done. When may we use code formatting on this site, except for code? I don't feel that marking up something as a quotation that isn't one is semantically correct, either.
Comment: For the most part, you shouldn't be using code formatting unless it's for code. There are only a few exceptions, like maybe file names, since even the punctuation is important there. Using blockquotes is the best option for (extended) text that you created to sound like you were quoting from another source, and it's used extensively that way on sites like ELU and ELL.


How important is publication for PhD admission?

Question: As a master's student in computer science, I would really like to go for a PhD at a good CS department. However until now, I have no publications and really have no idea how to start research. I'm interested in many subjects but I have not yet been able to narrow down the choice to a specific one. For someone like me who just began his or her master's studies and wants to plan for a PhD, what is the real number one priority besides a good GPA?
Comment: In academia the currency is publications. In your PhD, you are expected to produce that currency out of thin air. If you have a dime on day #1 in your pocket, it certainly does not hurt you. However, what the admission committee will be thinking is your ability to produce some big $$.
Comment: In general I think it's quite field-dependent, but I believe any undergraduate or master-level publications help. Maybe not in predatory journals.
Answer: I would say publications dont matter to start with a PhD, in general. Having them might help in reducing length of your PhD.
A good thing to have is liking for one area in CS, and good knowledge in that area atleast. e.g. systems or security or algorithms or formal verification or databases or distributed systems etc. Later when you join for the PhD program, you will do courses and talk with people to get an understanding on what is a good research problem etc.
Comment: _I would say publications dont matter to start with a PhD, in general._ — You may be right _in general_ but in strong departments (like mine), having publications is a significant advantage when applying for a PhD, and a de facto requirement if the applicant already has a master's degree.
Comment: Except if the particular PhD program does not involve any course work.
Answer: If your Masters degree is a degree by research then you'll already be starting down the road of learning just how to carry out a research project. So you're in the typical position of most undergrads transitioning to postgrad studies. At that stage it would be quite unusual for you to have been able to contribute to a research paper (based on my experience working in universities in the UK, Germany and Australia).
As you progress through your Masters you will hopefully have the opportunity to investigate areas which may interest you, and narrow down which field(s) might suit your intentions to pursue a further degree. Perhaps during this time you will contribute to some piece of research which will be published before you graduate. Given the timescales involved in academic publishing though this is unlikely unless you, join and make a final contribution to, an established project (for example). This would possibly make you stand out a little more when applying for doctoral positions, but it would not be essential. Masters level research frequently does result in publications, but these may come out some years after you complete the degree (depending on the field of course)!
If your Masters does not have a research component then you will have to make some time to do some independent reading, study recent publications in your field etc and get a sense of what research groups / professors exist whose interests would match yours.
The number one priority would definitely be defining and establishing your interests. So you want to find out what in CS you are enthusiastic about and committed to investigating, and be able to demonstrate that genuine enthusiasm when applying. A good PhD student is in effect a colleague in training rather than a student to be taught, and you want to be able to show that's what you have the potential to become.
This, I admit is a somewhat idealised view of what I would want to see in a prospective PhD student. Where you're located, which universities you wish to apply for, and how they deal with admissions (among other things) will all have specific impacts on what is important. So you'll have to discover, and tailor your preparation to, those criteria too!


How to remove default "web server (HTTP)" outgoing port from Routing and remote access windows 2012 server

Question: Added print screen where windows add default firewall port forwarding rules ant not allow to remove them. It is possible to remove or change outgoing port?
Answer: Just add a new 'Service' and call it whatever you like with whatever port you want. The services you're looking at are for standards and the HTTPS standard is TCP/443 and HTTP is 80/TCP. That's why you can't change it.
Comment: same port not allowed.


Question on surds rule

Question: Through the textbook, I've been taught the rule $\frac{\sqrt a}{\sqrt b} = \sqrt\frac{a}{b}$, however I realized that if all numbers are assumed to be real, and $a<0 ,b<0$, then the rule is not true as $\frac{\sqrt{-a}}{\sqrt{-b}} = \sqrt\frac{a}{b}$, whereas in $\frac{\sqrt{-a}}{\sqrt{-b}}$, the process makes it invalid as square rooting negative numbers is impossible. So does this mean that the surds rule (multiplication of surds included) is invalid for negative numbers? Or does it mean complex numbers have to be introduced in all cases?
Comment: If you look closely at the textbook source for this rule, it is likely that it specified $a$ and $b$ must be greater than or equal to $0$. An instructor might not always stress that restriction. And in many application scenarios, the values of $a$ and $b$ would naturally be positive, so the restriction wouldn't be important to stress.
Comment: @alex.jordan: You are wrong about that. I have seen countless textbooks actually used in schools that don't care one bit about getting mathematics correct.
Answer: For all nonnegative real numbers $a$ and $b$ (with $b > 0$), we have
$$ \frac{\sqrt{a}}{\sqrt{b}} = \sqrt{\frac{a}{b}}. $$
After that, all bets are off.  The basic problem is that the function $x \mapsto x^2$ is not injective (one-to-one) over the real numbers.  Thus to define the principal square root, which is what the surd represents, we must restrict the domain of this function to the nonnegative real numbers.  Thus if we are working with real variables, then, for example, $\sqrt{a}$ is nonsense for $a < 0$.
Okay, so real variables cause problems.  What if we work with complex variables, instead?  Unfortunately, even if we are careful, we generally cannot get the "surd rule" to work as you want.  For example, if we could extend it, then we might have
$$ 1 = \sqrt{1} = \sqrt{(-1)^2} = \sqrt{-1}^2 = i^2 = -1, $$
which is clear nonsense.  The problem again comes down to how we define the square root function, and on what domain that definition holds.  There are generally two possible choices, and these choices are more or less arbitrary.
Comment: *Principal* square root aka positive square root.
Comment: @inéquation Indeed.  Thank you.
Answer: The main problem is $\sqrt{\cdot}$ isn't defined for negative values as you've pointed out. While you can find numbers that square to negative numbers using the complex numbers, the problem is that there's no natural way to choose them. That is to say, $i$ and $-i$ are essentially indistinguishable (I mean mathematically. Our notation allows us to tell them apart, but we essentially just picked one of the two at random and called that one $i$ and the other one $-i$. It didn't matter which one we named which.) Thus while you can define a continuous function, $s: \Bbb{R}\to\Bbb{C}$, such that $s(x)^2 = x$ for all $x\in \Bbb{R}$, say by
$$s(x) := \begin{cases}\sqrt{x} & x\ge 0 \\ i\sqrt{|x|} & x < 0, \end{cases}$$
if you check to see whether this satisfies $s(xy)=s(x)s(y)$, or $s(x/y)=s(x)/s(y)$, you'll see that it fails to satisfy either except in special cases.
Comment: @StellaBiderman If I were being more technical, I would just say the issue is that $z\mapsto z^2$ is a 2-sheeted ramified covering map, I would still say that $\sqrt{z}$ isn't defined. Though we can find local inverses of course.
Comment: @infiniteaccelerator0643 I was in the middle of editing my answer to give the "real answer" given here. Since this has been posted, I've deleted my answer. My one qualm with jgon is that I would say that $\sqrt{x}$ is defined everywhere, it's just multivalued and not a function. We pretend it's a function by looking at it on positive values and declaring that we want to get a positive output. We can do this because the order on $\mathbb R$ lets us distinguish $-1$ and $1$. But as jgon says, the same can't be said of $-i$ and $i$.
Answer: You should start with the definition of the square root and the set of numbers you are working in.  In the reals $\sqrt x$ is only defined for $x \ge 0$ and the result is defined to be nonnegative.  That makes it a well defined function and the rule you cite depends on that.  If you are working in the reals and $a,b \gt 0$, $\frac {\sqrt {-a}}{\sqrt {-b}}$ is undefined.  Whether you can make sense of it by going to the complex field is immaterial.  There is a temptation to say $\sqrt {-a}=i\sqrt a$ but there is no way to distinguish that from $-i\sqrt a$.  This can be useful for exploration of problems, because it does not always cause a problem.  If you use it, you need to get rid of it in your final answer.  If you are working in the complex numbers $\sqrt a$ has an infinite set of values until you choose a branch of the square root.  The identity you quote does not hold any more because of the branch choice.
Answer: Even if you define the square-root on all real numbers such that $\sqrt{-1} = i$, you will still not have any such property, otherwise:

(WRONG) $\dfrac{1}{i} = \dfrac{\sqrt{1}}{\sqrt{-1}} \overset{???}= \sqrt{\dfrac{1}{-1}} = \sqrt{-1} = i$ and hence $1 \overset{???}= i^2 = -1$.

Bottom-line: You should make sure your textbook is a mathematically proper one, and also try not to simply memorize mathematical 'facts'. Every theorem in mathematics has a proper proof, and the more rigorous mathematics you learn the more you will understand that there is no such thing as a random 'law' to be followed.

Question on surds rule


UK company denies an explanation to a rejected candidate, alleging proprietary system

Question: In the UK, can a company deny explaining the reason why a prospective candidate was rejected, just because it allegedly uses a proprietary system to vet job seekers?
Comment: The standard for legal reasons is not to give a reason its the same with formal references
Comment: What exactly will you do with the information that they give you? They don't want to hire you, getting a court order to force them (assuming that you go through the legal grind and win) is not as good an idea as it sounds to some sue-friendly people. :P
Comment: I'll just add that if bringing them to court, you should not expect that to be a highlight in further job interviews, nor should you expect that the threat of suing them will get them to change their minds and hire you. Remember that a lot of industries are small well-informed network: it's very hard to correct a bad reputation in an industry.
Answer: The company doesn't owe you any explanation whatsoever why it is rejecting you. If you suspect they are rejecting you because of illegal discrimination, you could take them to court - but proving that would be almost impossible unless the company acts totally stupid.
In court they can't refuse to tell why you were not hired. Your risk is that the interviewer might say "Mr. Ajram had spinach between his teeth from lunch, which made me sick, so I didn't hire him". Which would be a perfectly legal reason not to hire you, and would mean that you lose the case probably with substantial cost.
Others noted that you can ask the company to provide all the information they stored about you. They have no obligation to store anything about you. They might even be allowed to respond "we received your request, we deleted all information about you except a note 'interviewer recommended not to hire', and this note is all the information we have stored about you".
Comment: @M.Ajram What they have to say in court is more of a legal question. Find a lawyer or try law.stackexchange.com
Comment: So, unless someone within the company admits it, the whole is pointless? If taken to court, could it still deny any explanation due to the same reason?
Answer: Under the Data Protection Act, you can request access to e.g. interview notes (e.g. see https://www.theguardian.com/careers/careers-blog/what-data-employers-hold-on-you-philip-landau). For government related employers like BBC, GDS it should be easy to get these data. For private sector employers I'd guess your mileage will vary.
However, I don't think you can force the company to give a reason for the rejection (although I'm not a lawyer).
Comment: It's not as easy as you may think. I am not a lawyer, but if, for example, interview notes are taken in a notebook and not subject to a "well structured" filing system, you may be out of luck.
Comment: Or if the interviewer took no notes, or destroyed them. You have the right to know what information they have stored about you. Which may be nothing.
Comment: @LaconicDroid: It is apparently in fact easy for government related employers like BBC, GDS because they care a lot about compliance. I know someone who got their interview notes from these companies. I agree re: private employer though.
Comment: Getting all the information they have about you shouldn't be a problem for any company. However, there might just be no interview notes. They are not required to keep such notes, quite the contrary.