Confidence Intervals for Elasticity in Simple Linear Regression

Question: I'm pretty sure this is a very simple question that I am missing something obvious. I have a simple linear regression with multiple independent variables. I want to calculate the elasticity (no problem - $\frac{\partial y}{\partial x} \cdot \frac{x}{y}$), but also report the confidence interval for the elasticity. I know it's straightforward to compute the confidence interval for $\beta$ ($\hat{\beta} \pm t^{*}_{\alpha} \cdot \sigma_{\beta}$ ). But for the confidence interval for the elasticity, would it be the same range? Or do I need to account for the transformation ($\beta * x/y$)?
Answer: If I understand correctly, what you are proposing is estimating:
$$y = \gamma_0 + \gamma_1 \cdot x + \xi $$
and then using the confidence interval of $\gamma_1$ to estimate the range of elasticities:
$$ [\frac{\gamma_1 - 2 \cdot \sigma{\gamma_1}}{y} \cdot x, \frac{\gamma_1 + 2 \cdot \sigma{\gamma_1}}{y} \cdot x] $$
This is wrong, essentially because of Jensen's inequality ($E[f(x)]\neq f(E[x])$). You should absolutely take into account the non-linear uncertainty when calculating the confidence interval. Fortunately, this is easy. If you run the regression estimate of $$\ln(y) = \beta_0 + \beta_1 \cdot \ln(x) + \epsilon$$
then the confidence interval of $\beta_1$ is the confidence interval of the elasticity.
In follow up discussion, the questioner asks if it is possible to do this with the linear regression coefficient ($\gamma_1$), along with $\bar{x},\bar{y}$ and the associated standard errors? Why would you want to know the elasticity at the average values instead of the average implied elasticity over all x-y pairs? The beta parameter is estimated on the full population so why not the elasticity too? Because all we only know the average values and the linear regression coefficient.
In principle, you can do a Monte Carlo simulation like the following:
$$ \hat{elasticity}= (\hat{\gamma} + SE_{\gamma} * N(0,1)) * (\bar{x}+ SE_{\bar{x}} * N(0,1)) / (\bar{y}+ SE_{\bar{y}} * N(0,1))$$
do a bunch of simulations, and use this to make a confidence interval around the elasticity estimate.
In simulations that I ran, this did result in 95% standard errors that included the true value, but that might simply be a function of the parameters I tried. Unsurprisingly, the resulting standard errors on the elasticity are much larger than in log specification.
Comment: Why would you want to know the elasticity at the average values instead of the average implied elasticity over all x-y pairs?  The beta parameter is estimated on the full population so why not the elasticity too?  Or is it just that we only know the average values and the linear regression coefficient?
Comment: Thanks so much for your reply. Sorry if I was confusing - I was not proposing that for the confidence interval. I was saying that I know calculating the confidence interval for beta is straightforward, but not so for the elasticity unless I run a log log regression. In a situation where you just have the linear regression, how do you computer the confidence interval for elasticity (i.e., B*x/y)? As a note, I am using the means for x and y, and of course those have standard deviations etc...
Comment: yes exactly - that is all we know.


Render blocks in custom page

Question: I followed steps given in this link to create a custom Page.
Page is created and 'Hello world' is printing in the page, now i want to render some blocks in that page. How can I achieve this task?
Comment: Context is in D8 still alpha and you don't need it, because the block layout is now in core.
Comment: If you are not looking for a coding approach this can be achieved easily with [Context](https://www.drupal.org/project/context).
Comment: The question is a little vague - but, I'm assuming because the work "render" was used, @kenorb is attempting to place  a block via the Render API.

If that's the case "Context" has nothing to do with it.
Answer: Given that you're using a custom controller for your page, you have the option to load the block from your controller, or place the block in another region outside of that part of the page that the Controller controls.
For blocks such as global elements such as headers and footers, I would recommend you place them through the CMS at /admin/structure/block
For blocks that sit above or below the content that your controller loads, you can also place them from /admin/structure/block or you can load them from within the the controller.
If you need to place content above and below your block, you'd probably want to load it programmatically in your controller.
Here's a guide on loading blocks programmatically.
basically in your myPage() method that is returning the build array, you'd want the build array for the block you want to load.
<code>$build['events'] = \Drupal::service('plugin.manager.block')
  ->createInstance('my_events_block')
  ->build();

$build['recent_insights'] = \Drupal::service('plugin.manager.block')
  ->createInstance('recent_articles', ['title' => 'Some Recent Articles', 'offset' => 0])
  ->build();

return $build;
</code>
The code above works for the types of blocks that you custom create in your module, such as at /mymodule/src/Plugin/Block/RecentArticles.php
It doesn't work for loading an instance of a block that was created through the CMS.
For those you need to use:
<code>$block = \Drupal::entityTypeManager()->getStorage('block')->load('myblock');
$build['myblock'] =  \Drupal::entityTypeManager()->getViewBuilder('block')->view($block);
</code>
Answer: To render block on your custom page, go to Structure, then Block Layout, from there you can either create a custom new block (enable Custom Block for that), or configure the existing block. To place on your page, in Configure page, go to Pages under Visibility section and add path of your custom page to the list, then save. Your block should be shown according to assigned region.
If your custom page uses Twig template, see: How to render a template in Drupal 8.
If you'd like to create your own block programatically, see: Block API overview.

Render blocks in custom page


How to get projectile direction vector in a 2d grid?

Question: I am having trouble figuring out how to trace the path of my projectiles in an Asteroids clone. Currently the ship is locked to the center of the screen and can be rotated a full 360 degrees. I know the angle the ship is pointing at any given time, but I am not sure how to calculate the vector that the projectile should use for its trajectory. I know that I can find the correct vector by subtracting the end point from the start point.. but the issue is that I do not know the end point. Theoretically.. the end point is whenever the projectile touches the edge of the screen or some object. This is the current game code: https://jsfiddle.net/m6sxrk8w/
 just using a hardcoded movement vector of {x:-1, y:-1}. Can anyone give some advice on how to dynamically determine the true vector given the current direction of the ship? There must be some simple math I am missing here...
Answer: To find the unit vector from the angle you want to use cosine(angle) for the x-component and sin(angle) for the y-component.  The angle must be in radians.  You can convert from degrees to radians by dividing degrees by 180 * PI.
<code>radians = degrees / (180 * Math.PI);
x = Math.cos(radians);
y = Math.sin(radians);
</code>
Comment: So for example, if the ship is pointing at a .9 radian angle from the y-axis... the direction movement vector would be {x=cos(.9), y=sin(.9)} ?
Comment: Yes, and it's a unit vector, meaning it has a length of 1.  So you can scale it for distance / velocity or whatever you like. position.x += cos(radian) * distance;
Comment: They both should be correct.
Comment: So the formula you suggested works.. but for some reason it is always shifted by 90 deg. I am setting the x,y vector like so:

`projectiles[i].x += Math.cos(toRads(ship.direction));
 projectiles[i].y += Math.sin(toRads(ship.direction));`

I guess I have to somehow shift this result by 90 deg to actually get the correct direction? For example when my ship is pointing at 0, the shot goes in the 90 direction, when I am pointing at 90, the shot goes straight down to 180
Comment: It sounds like the front of your ship in your image isn't facing angle 0.  So you can rotate the image to face right, or yes simply add/subtract from the angle before you convert it to radians.
Comment: Its facing directly up on the screen. The rotation code based on that seems to work fine. But yes, I can just do the math and fix it. Thanks
Answer: This is a maths problem that I had myself  a few years ago.
You have two 2d vectors in pixel coordinates:
shootOrigin=(centerX,centerY);
mousePosition=(mouseX, mouseY);
shootDirection = Vec2.Normalize(mousePosition-shootOrigin);
The normalization of the 2d vector is very important here to get the bullets to travel at constant speeds. when shooting a projectile you just say bulletPos=bulletPos+shootDirection; every update frame and then check if the Vector2.Distance(bulletPos,enemyPos); from enemy to bullet is smaller than certain value.
I totally recommend you to read the first chapter of the book "Programming Game AI by Example" because its about the maths behind npc agents and basically how to use vectors for game development.
EDIT: I just saw its about rotating the ship with keyboard input so you just modify the angle of the ship instead of using the mouse as the shooting direction and therefore need to calculate the direction vector x,y from radians angle like suggested. The principle stays the same: calculate the normalized direction vector and apply it every frame to the bullets position. If you spawn a bullet it is even better if you create an bullet object that knows its velocity, direction and has an updateMove method implemented, otherwise your bullets will be rotated while flying because the direction might change through user inout (arrow keys).


Will 2 x 10 speed front derailleur work with 11 speed set up?

Question: Would an existing 2x10 front mech work with a new 11 speed rear set up? Using all Shimano SLX with 11 speed shifter, rear mech and chain. Front chain rings are 2 x SLX 38/28.
Answer: 11 and 10 speed cranksets have slightly different chainring spacings to accommodate the difference in 11 and 10 speed chain widths. Front derailleurs have slightly different movement also.
You have a matching 10 speed front derailleur and crankset, so really the question is whether an 11 speed chain will work on a 10 speed front. I think from past answers I have seen here it will work OK.
Comment: Also, be certain to check really carefully that the narrower 11-speed chain can't fit into places on a 10-speed crankset that it's not supposed to go - like between the two chainrings, or between the outer chainring and the right crank arm.  That's not likely to be a problem as there's really not that much difference between an 11-speed and a 10-speed chain, but you really don't want to find out the hard way that it **is** a problem.
Answer: It won't work well. It will be able to be adjusted such that it can physically move the chain from ring to ring, but it will be hard or impossible to get it and keep it adjusted so that there's no rub, no sluggish/hesitant shifting, and no propensity for chain drop.
Front derailer cages are matched to chain width, so in this case the cage will be wider than ideal. What tends to happen here is at the point where you have the inner cage adjusted close enough to the left side of the chain at its starting point for it to shift nicely up to the large ring, you'll then have too much gap on the other side of the chain once you're there, potentially causing derailment. You can try to use the high limit to mitigate this, but then it will shift badly if at all and over-stress the shifter mechanism (the cable will be statically stretched since the derailer wasn't able to move all the way, which puts a lot of force on the shifter mechanism when you try to release it, and accelerates shifter wear). And when you shift back down, the outer cage is further away from the chain than it should be, creating a clumsy shift.
Triples make the problem much worse. Doubles are still enough to force the qualty of the adjustment to be compromised. You can try bending around the derailer, but it doesn't tend to be really successful for this purpose, and then you're left with a mangled FD.
You can find lots of writing out there that downplays the significance of front derailer cage width. It's frequently parroted, and the degree to which it can be made to kinda sorta work enough for people to talk themselves into believing it's fine serves to reinforce the idea. But it's really not fine from a performance and probably enjoyment standpoint.
Comment: @AndrewHenle With respect, tolerances this small matter with front derailer setup, for better or for worse. Whether it's a dealbreaker or not is ultimately up to the user, but the performance will be affected in the way I describe.
Comment: IMO you're overstating the issues.  A 10-speed chain is 5.9 mm wide, an 11-speed chain is 5.4 mm.  That's a mere 1/2 a millimeter - or about **two hundredths of an inch**.  Again - a mere **0.02"**.  (Actually, it's even a bit *less* than that.)  That's all.  The crankset and chaining is going to flex way more than that under each pedal stroke if you're heavier than, oh, probably about 20 pounds.


Difference in statistics from Google Analytics Report and BigQuery Data in Hive table

Question: I have a Google Analytics premium account set up to monitor the user activity of a website and mobile application.
Raw data from GA is being stored in BigQuery tables.
However, I noticed that the statistics that I see in a GA report are quite different the statistics that I see when querying the BigQuery tables.
I understand that GA reports show aggregated data and possibly, sampled data. And that the raw data in Bigquery tables is session/hit-level data.
But I am still not sure if I understand the reason why the statistics could be different.
Would really appreciate it if someone clarified this for me.
Thanks in advance.
UPDATE 1:
I exported the raw data from Bigquery into my Hadoop cluster. The data is stored in a hive table. I flattened all the nested and repeated fields before exporting.
Here is the hive query that I ran on the raw data in the Hive table:
SELECT
   date as VisitDate,
   count(distinct fullvisitorid) as CountVisitors,
   SUM(totals_visits) as SumVisits,
   SUM(totals_pageviews) AS PVs
FROM
   bigquerydata
WHERE
   fullvisitorid IS NOT NULL
GROUP BY
   date
ORDER BY
   VisitDate DESC

A) Taking February 9th as the VisitDate, I get the following results from this query:
i) CountVisitors= 1,074,323
ii) SumVisits= 48,990,198
iii) PVs= 1,122,841,424

Vs
B) Taking the same VisitDate and obtaining the same statistics from the GA report:
i) Users count = 1,549,757
ii) Number of pageviews = 11,604,449 (Huge difference when compared to A(iii))

In the hive query above, am I using any wrong fields or processing the fields in a wrong way? Just trying to figure out why I have this difference in numbers.
UPDATE 2 (following @Felipe Hoffa 's suggestion):
This is how I am flattening the tables in my Python code before exporting the result to GCS and then to Hadoop cluster:
queryString = 'SELECT * FROM flatten(flatten(flatten(flatten(flatten(flatten([' + TABLE_NAME + '],hits),hits.product),hits.promotion),hits.customVariables), hits.customDimensions), hits.customMetrics)'

I understand what you are saying about flattening causing repeated pageviews and each repetition getting into the final wrong addition.
I tried the same query (from Update1) on Bigquery table instead of my Hive table. The numbers matched with those on the Google Analytics Dashboard.
However, assuming that the Hive table is all I have and it has those repeated fields due to flattening.. BUT Is there still anyway that I can fix my hive query to match the stats from Google Analytics dashboard?
Logically speaking, if the repeated fields came up due to flattening.. can't I reverse the same thing in my Hive table? If you think that I can reverse, do you have any suggestion as to how I can proceed on it?
Thank you so much in advance!
Comment: Could you please share some numbers and query that you used to have this conclusion. Without specific info, we don't know if the query is written wrong or something else is going on. Also you can reach out to your paid support.
Comment: @Pentium10 My apologies for partial information. I updated my question. Thanks!
Comment: Note that the returned value for DISTINCT is a statistical approximation and is not guaranteed to be exact. Other than this I don't see any obvious miss. Read count distinct here https://cloud.google.com/bigquery/query-reference
Answer: Can you run the same query in BigQuery, instead of on the data exported to Hive?
My guess: "The data is stored in a hive table. I flattened all the nested and repeated fields before exporting." When flattening - are you repeating pageviews several times, with each repetition getting into the final wrong addition?
Note how data can get duplicated when flattening rows:
SELECT col, x FROM (
  SELECT "wrong" col, SUM(totals.pageviews) x
  FROM (FLATTEN ([google.com:analytics-bigquery:LondonCycleHelmet.ga_sessions_20130910], hits))
), (
  SELECT "correct" col, SUM(totals.pageviews) x
  FROM [google.com:analytics-bigquery:LondonCycleHelmet.ga_sessions_20130910]
)

col     x
wrong   2262
correct 249

Update given "update 2" to the question:
Since BigQuery is working correctly, and this is a Hive problem, you should add that tag to get relevant answers.
Nevertheless, this is how I would correctly de-duplicate previously duplicated rows with BigQuery:
SELECT SUM(pv)
FROM (
  SELECT visitId, MAX(totals.pageviews) pv
  FROM (FLATTEN ([google.com:analytics-bigquery:LondonCycleHelmet.ga_sessions_20130910], hits))
  GROUP EACH BY 1
)

Comment: Please check my update #2 in my question above. Thanks. @Felipe Hoffa
Comment: Thank you for all the prompt help. I realized that even with de-flattenizing queries, I had a problem with the stats because there were embedded commas and newlines within my hive table. I could clean up the embedded commas and I now have really really close stats stats. I cleaned up the embedded commas using CSV SerDe in my hive query.
Comment: Is there any way that I could remove these embedded commas and/or new lines at the stage where I am exporting my destination table from BigQuery to GCS? Ideally, I would like to replace these embedded commas and newlines with custom delimiters, which would not be parsed incorrectly by Hive when I load this data into a Hive table.
Comment: I would make that a different question - needs more context.


Keyboard input vs character movement encapsulation

Question: In our game created with c++ and sdl we are having difficulty delegating how the main character should be controlled.  We have a keyboard class and a sprite class for the main character, but are unsure if the main character should have an instance of the keyboard class or if keyboard input should be done through the game loop.  If you need anymore information I would be happy to provide it, thanks in advance for any help.
Answer: Your main character class should not have a reference to the keyboard or any input-related class.
Input should be handled in the game loop, or preferably a dedicated input class, decoupled from other entities so they'll only need to respond to abstract actions, not raw input.
Not all input is related to your characters and and not all types of input devices are the same, so your best bet is to separate the input handling into several stages so you can handle it contextually e.g.

Gather input data
Examine current game state or context (MainMenu, InGame, InGameMenu, GameOver etc.)
Mapping raw input to actions
... etc.

This will make it easier for you to implement new actions, control schemes, input devices or multiplayer controls.
Comment: How does the transition from the input class to the main character work?  Is the data sent from the input class to the main character in the game loop?
Comment: Depends on you architecture. Yes, the simplest way would be to listen for input in the game loop and map it with something like map. For more elaborate designs you can take a look at these: http://gamedev.stackexchange.com/questions/59582/input-management-techniques-in-large-games , http://gameprogrammingpatterns.com/command.html


Didn't Voldemort also survive the killing curse?

Question: In Harry Potter and the Philosopher's Stone, Harry and his parents were attacked by Voldemort and Harry's parents died. But Harry survived because his mother had died to save him and as a result Voldemort's killing curse had rebounded upon him. But that is weird because if Harry is the only one to have survived the killing curse then Voldemort should have been dead. This leads me to think that Voldemort was able to survive the killing curse as well and so Harry wasn't the only one to survive it.
Comment: Does this answer your question? [How has no one else ever survived the Killing Curse before Harry?](https://scifi.stackexchange.com/questions/93358/how-has-no-one-else-ever-survived-the-killing-curse-before-harry)
Comment: In the class on Killing Curses, fake Moody says that everyone could cast the Killing Curse on him at the same time and he'd be fine. This, to me, explains why most Death Eaters choose not to attempt it, and only people like Voldemort use it because it's his "signature" spell. The only missing piece is why no one attempts it and fails, like Harry did with Crucio against Bellatrix, or fake Moody with Imperio against Harry.
Comment: I reopened this question because while the titles are similar, it actually seems to be a fundamentally different question. The other question asks how Harry's situation had never occurred before, while this question asks whether a certain "fact" is evidence that Voldemort did not survive. Indeed, none of the answers to the other question address this, and the only answer that even mentions that Voldemort survived is deleted with comments saying that it doesn't answer *that* question. (I don't think it would really answer this question in any real sense either, except to reassert a premise.)
Comment: Harry was credited to be the only killing-curse survivor while everyone thought voldemort was dead.
Answer: The Dark Lord did indeed survive it as well.
It is indeed correct that the Dark Lord survived the Killing Curse as well. He mentioned this himself when addressing the gathering of Death Eaters in the graveyard.

"You know my goal – to conquer death. And now, I was tested, and it appeared that one or more of my experiments had worked … for I had not been killed, though the curse should have done it." - Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)

Though it remains a rare occurrence, it is true that Harry was not the only one in history to survive the Killing Curse. The Dark Lord was able to survive the Killing Curse because he had Horcruxes, which tethered his soul to earth so he could not truly die even if his body was destroyed.

"Well, you split your soul, you see,' said Slughorn, 'and hide part of it in an object outside the body. Then, even if one's body is attacked or destroyed, one cannot die, for part of the soul remains earthbound and undamaged. But, of course, existence in such a form …'
Slughorn's face crumpled and Harry found himself remembering words he had heard nearly two years before.
'I was ripped from my body, I was less than spirit, less than the meanest ghost … but still, I was alive.'
'… few would want it, Tom, very few. Death would be preferable." - Harry Potter and the Half-Blood Prince, Chapter 23 (Horcruxes)

Wizards who have created Horcruxes are themselves very rare, so it would be unlikely that many others have survived the Killing Curse in this way, but the fact remains that the Dark Lord did.
Answer: I think that when you say that:
"Harry is the only one to have survived the killing curse,"
you have in mind this quote said by the fake Mad-eye Moody in Harry Potter and the Goblet of Fire.:

"There is only one person known to have survived it (the killing curse). And he's sitting in this very room."

But I would like to draw your attention to some points to show that what Barty Crouch Jr. (the fake Mad-eye Moody) may have said was not entirely true.
After the mishap of the Godric's Hollow, no one knew what actually happened to Voldemort. Voldemort certainly had vanished but none had a clue if it was due to the rebounding killing curse or something else. Now when Barty Crouch Jr., a devoted death-eater, found his master, he most probably did not ask him about that night (he was a true servant and would never ever want his master to relive that horrific night).
There can be another explanation. Even if Barty Crouch Jr. came to know how his master disappeared, why would he carelessly tell this to anyone and attract attention to the fact that how much he knew about what happened that night (especially when his master was weak and needed his support in complete isolation from the wizarding world).
So, you are right in thinking that Voldemort too survived the killing curse (because of his horcruxes) and what the fake Mad-eye Moody said is not right.
Comment: No, what he said was true. Harry was the only person **known** to have survived the killing curse. People didn't **know** that Voldemort had survived. (Although it's not entirely clear how Harry is **known** to have survived it. Seems like people coming to the conclusion that Voldemort had cast it on him is inference, since the only people who were there were the Potters and Voldemort.)
Comment: Harry and Voldemort also both simultaneously survived the killing curse in Goblet of fire
Answer: No Voldemort also survived the killing curse; because he had horcruxes. I know what you're thinking:

There is only one person known to have survived it. And he's sitting in this very room

Well that Moody was fake and it was unclear as to what happened that night prior to that lesson
Answer: It may not have been known that the curse rebounded on Voldemort
In Chapter One of Philosopher's Stone McGonagall says the following to Dumbledore:

No one knows why, or how, but they're saying that when he couldn't kill Harry Potter, Voldemort's power somehow broke — and that's why he's gone."

It seems clear that she does not know that the curse rebounded on Voldemort. Moreover, Dumbledore doesn't tell her that that's what happened, which would likely indicate that either Dumbledore didn't know either, or he wanted it to be kept secret.
Three chapters later we find the following exchange between Harry and Hagrid:

"But what happened to Vol-, sorry — I mean, You-Know-Who?"
"Good question, Harry. Disappeared. Vanished. Same night he tried ter kill you. Makes yeh even more famous. That's the biggest myst'ry, see... he was gettin' more an' more powerful — why'd he go?

Notice that Hagrid doesn't give any information about what caused Voldemort to disappear. Again, it seems that average members of the Wizarding community such as Hagrid were simply unaware of what actually happened.
Thus, the claim that Harry was the only person to survive the Killing Curse should not be taken as evidence that Voldemort did not survive. It may simply be that those promulgating this fact were unaware that Voldemort had been hit by a Killing Curse.
Comment: I don't understand the downvote. This is the correct answer: Given what the magical community knows, Harry *is* the only one who survived a killing curse. The rebounding of the spell and the whereabouts of Voldemort are unknown.
Answer: I have to disagree with the submitter's understanding.  When the curse rebounded, Voldemort's body died, and what was left of his soul split in two, one piece latching onto Harry, the other wandering in the wilderness (until Quirrell came along).  To my mind, that doesn't entirely count as 'surviving' in any reasonable sense, as contrasted with baby Harry, whose body and soul were still alive and undamaged (save for the scar).


Who is my ancestor?

Question: According to the Bhagavad Gita, I am a soul; not my body. Souls are parts and parcels of God (or for advaitins, souls are God).Souls transmigrate from one body to another(2:13), but the material body perishes. Who then is my ancestor referred to in chapter 1, verse 41? Also, it is implicit that one soul can help another after the latter has left its body (by performing certain rituals; 1:41). Can a soul help another with its karmic burden?
Comment: You mean souls transmigrate from one dead body to another new born body?
Answer: God is believed to be the recipient of all fruits of all action. Your ancestors have given and and received karma phalams  through a "divine Corpus Fund" by such routing but individual "trading" does not always succeed.
Some great souls who attained spiritual liberation have the capacity to take the energy/phalam on themselves and re-distribute to the deserving but Karma phalam cannot be transferred  either as reward or punishment for and by ordinary souls through  individually maintained "savings accounts"... it is into the Corpus Fund that all action credit goes in and gets redistributed in a mysterious way.
This message runs throughout Chapter 5 of Bhagavad Gita. Verse 8-9 in particular  enjoins anyone with such communion as one already liberated, blessed with a joy to go further on with an assurance that whatever happens is quite acceptable.

Who is my ancestor?


How can I keep the same position for my objects?

Question: I want to photograph the front and the back of my objects. But when I turn around my object, it isn't in the same position anymore und it will move a bit. What can I do to keep the exact same position? I'm shooting product photos.
Comment: Hello ercMatha, welcome to Photo.SE. Can you post a picture of your setup ? What process would you like to achieve ?
Answer: First of all: if you really want precision. I mean precision that one picture matches the other "pixel-perfect". I have to disappoint you because this is nearly impossible. However there are solutions that bring you close:
Solution 1: use a Template
This is very fast and produces very accurate positioning. The drawback is  that you first need to "construct" a template and it is therefore only valuable if you have a series of similar objects.
Prerequisites:

Put your camera on a heavy tripod or fixed position.
create a template where your objects fit. This can be done from wood, cardboard or even paper. You could also use multiple different templates that fit the objects in different ways (frontside, backside, upside-down etc...) but all at the correct position.

Working steps

place the template
align the object with the template
remove the template
shoot the photo

Solution 2: Projector
This is the "electronic evolution" of the first solution. LED projectors have become cheap nowadays. It does not need to be a high quality projector - any cheap $100 LED or LCD projector will do. Smaller size can be an advantage.
With a projector, there are multiple possibilities to help you positioning your objects.

as in solution 1, use a tripod for your camera
mount the projector. I see three possibilities:

mount the projector approximately above the camera onto the ceiling
mount the projector next to the camera onto the same tripod
use another tripod for the projector

Grid method:

project an image with a grid (like this) onto your object table
place and align the object along the grid
switch off the projector
shoot the photo

Picture method:

place the object onto the table
shoot a photo (but leave it in the position where it is)
project the image you just shot with the projector onto the object itself
remove the object and place and align the new object on the table
switch off the projector
shoot the next photo

Remark:
Since switching the projector on and off in short time can seriously reduce the lamp lifetime, you are probably better off just putting a cap onto the lens of the projector for the shoot. If you are taking photos with a flashlight, you probably do not need to care. (flashlight is much more bright than the projector).
Answer: Put markers where the object needs to be when turned around, to be aligned with the camera. Keep camera unmoved on a tripod.


Fallout Shelter save files location on Windows 10

Question: How do you find the fallout shelter vault save file on windows 10?
Answer: The save game files for Fallout Shelter for Windows 10 can be found in
%appdata%\Local\Packages\BethesdaSoftworks.FalloutShelter_3275kfvn8vcwc\SystemAppData\wgs\LONG_ENCRYPTED_CODE\ANOTHER_LONG_ENCRYPTED_CODE\your saves here
Common errors:

If you cannot see hidden files, go onto the 'View' tab within the Explorer, and tick 'Hidden items'.
If you cannot go into the packages folder, firstly right-click and go into 'Properties'. Then go under the security tab and click 'Edit' by the 'To change permissions, click Edit' text. You then have to click 'Add' after the pop-up comes up. In the text box, type your email address tied with your windows 10 account and click on 'Check names', if it is correct, it will allow you to continue into the folder after clicking 'Okay'.
Answer: Windows: %LOCALAPPDATA%\FalloutShelter\

Open the File Explorer
Paste %LOCALAPPDATA%\FalloutShelter\
Press Enter

Steam Play Linux: <Steam-folder>/steamapps/compatdata/588430/pfx/


What's the difference between dim and bright light?

Question: When comparing two light sources, for example, a light bulb at 20W and a light bulb at 100W, what is it about the incoming light that makes the latter look brighter than the former? Are there different reasons why different light sources looks different in brightness (High five for cramming three instances of "different" in the same sentence)? For example, in this thread, it is stated that the human eye is most sensitive around 555nm, something that I guess translates to meaning that given a light of the same intensity (whatever that means, hence my question), it is going to be perceived as most bright when hitting 555nm. Does this question have different answers depending on if you're seeing light as a particle vs a wave?
Answer: Brightness is just the number of photons per second hitting your eye - all the other properties of the light are the same.
edit: perceived brightness is the number of 'detected' photons hitting your eye per second!
Different wavelengths of light correspond to different  colours. 555nm means light with a wavelength of 555 nano-meters (billions of a meter), this is roughly green light. So all this says is that you eye is most sensitive to green light and so a given number of green photons/second will appear brighter than the same number of red photons.
You can see this with laser pointers, for the same power small pointers - green ones look much brighter than red.
Comment: Couldn't the keepers of this page program an insert to the comment parser field which says something on duality of light? That might be superfluous sometimes, but never wrong :=)
Comment: @Speldosa - there is a difference between the 'actual brightness' measured by some system and the 'perceived brightness' measured by your biased eye
Comment: This explanation lacks any sort of physical preciseness. It fails to mention the dual nature of light, for a start. It's not technically wrong, so I won't down-vote though.
Comment: What about the amplitude of the light? Is that just a measure for the amount of photons?
Comment: Also, doesn't the second paragraph contradict the first one? You show an example where brightness is *not* governed by the number of photons per second hitting the eye.
Comment: @Martin Beckett: Ok. I'm only interested in the subjective brightness.
Comment: on a similar lines, one can observe that CFL's having low wattage can produce much higher brightness(for human eye) than corresponding incandescent lamps.
Comment: oh, so if I have a camera that takes a picture instantly, it would be unable to take a picture because it needs exposure for a period of time for it to accumulate an approximation for the average intensities of many instants(to avoid infinitesimal paradoxes, very very short intervals of time) at a time?
Answer: The 100 W light bulb dissipates more energy per second (1 watt = 1 joule per second) than the 20 W light bulb, and consequently the light emanating from the 100 W bulb carries more energy than the light emanating from the 20 W bulb.
In the picture of light as an electromagnetic wave, the energy carried by the light is proportional to the square of the wave's amplitude. The technical term for this energy is "Poynting flux". (In fact we usually take the time-average over one period of oscillation as the definition of the energy in the wave.) In this model, the photo-receptors in your eye are oscillators. What is oscillating? Electric charge. Charges are accelerated in response to the electric field of the light: the greater the electric field (or amplitude), the greater the amplitude of the oscillation, and the greater the electric currents in your eye (and the greater the brightness).
In the picture of light as a particle (a photon), each particle carries with it an amount of energy proportional to its frequency: $E=h\nu$, where $h$ is Planck's constant, and $\nu$ is the frequency of light. The energy flux is then the energy per photon multiplied by the flux of photons (# of photons per unit area per second). So the 100 W bulb emits more photons per second than the 20 W bulb. In this model, the photoreceptors in your eye undergo chemical reactions as a result of absorbing photons. The more photons absorbed per second, the brighter the light appears.
Answer: I am nowhere near as expert as a professional, but I have a private passion for this field.
Dim and bright are perceptual terms.  There are many dimensions.  I will start with a simple idea and build out.
Consider that you are adapted to a monochromatic light of around 533 nanometer wavelength bathing the room such that the light from the brightest object generates approximately 1e7 photons per second on a foveal L cone of 1 micron face diameter.  This is considered a well-lit but not stressful scene.  The photoreceptor opsins bleach at a rate of approximately 5e3 opsins per second.  The light feels neither dim nor bright because you are adapted.
If you increase the source photon rate by a factor of 10, that same photoreceptor is now bleaching at a rate of 5e4 opsins per second.  This feels brighter.  But over time, the photoreceptor undergoes phagocytosis, decreasing its length by 90% changing the opsin bleach rate back to 5e3 opsins per second, so you now experience this as neither dim nor bright.
If you decrease the wavelength to 430 nanometers, the bleach rate of the L cone decreases by 90% and one would think this would appear dim.  However, the S cone bleach rate reaches its maximum and S cones have a stronger effect on perceived brightness than L cones, so without increasing the photon bleach rate, the light now appears to have gotten brighter.
This is the principal reason amber sunglasses make the world seem brighter and more colorful.  By suppressing the short wavelength photons from reaching the eye, the adaptation of the L and M cone bias favors a greater linear range.  This makes colors more discriminable and is another dimension of brightness.
I will leave these three dimensions for further discussion and, if requested, I will dive deeper yet into the wonderful world of retinal adaptation to various light regimes.


Latte Art... How much foam is too much foam?

Question: I've been a home coffee enthusiast for nearly 12 months now, so to cut a long question short, I'm pulling really nice & consistent espresso shots now after much experimenting & learning...but it's the latte art that is eluding me. I end up with what I think is way too much foam despite my attempts at keeping the stretch to a small amount. Does usually look smooth & silky at a good temperature & I my pouring is getting better all the time - but still the art will not show... Is it the milk?.. I'm only using supermarket bought full cream milk. Thanks !! :)
Comment: Hi, Steve. I can't tell what your actual question is, here. How much foam is too much is surely a matter of personal taste and it's not clear what problem you're attributing (possibly) to the quality of the millk.
Answer: Ideally for latte art you should have zero foam in the conventional sense i.e. coarse foam or froth that has easily discerned bubbles. What you want to achieve is to make a completely homogeneous pitcher of microfoam.


Do the Roman Catholic and Eastern Orthodox Churches observe different dates for Pascha?

Question: Someone claimed on another forum that the Roman Catholic Church and Eastern Orthodox Church observe different dates for the feast of Pascha/Easter. Is this so? If so, what does this imply about the unity of the Church?
Comment: The Eastern Orthodox Church goes by the Julian calendar; the Roman Catholic Church goes by the Gregorian calendar, also known as the Western calendar. That may contribute to the discrepancy between the dates.
Comment: @Anonymous: Interesting. I didn't know that.
Comment: @Anonymous The Gregorian calendar was not introduced until 1582.
Answer: Disagreement about the date for Easter goes back to the very earliest years of Christianity.  Pope Anicetus and Polycarp are said to have disagreed about the correct date, as early as the middle of the second century, both finally agreeing that they could not convince each other to change.  Irenaeus, bishop of Lyons in what is now France, mentioned this in a letter to Pope Victor, as a precedent to press Pope Victor to allow Eastern Christians to continue their tradition when they were in Rome.
Easter continued to be celebrated on different days in the east and in the west, but this was almost the least of the issues that divided Christianity. What today would seem to be a trifling issue, the insertion of the filioque clause into the Nicene Creed was to be the major issue that finally sealed the division of the eastern and western branches of Christianity, in the Great Schism of 1054. Pope Leo XI insisted on inserting the filioque clause, providing a subtle change in the definition of the Trinity, into the Nicene Creed in spite of a requirement that no change could be made to the Nicene Creed other than by a council of the bishops. Another trigger was that the western churches insisted on celibacy for the clergy, whereas the eastern churches regarded marriage by the clergy as acceptable.
While the disagreement about the date of Easter may be about genuine, firmly held views on proper theology, many of the other divisions that occurred in the Christian Church have been about power. Pope Leo was arguably more concerned to assert his authority over the entire Christian Church than whether priests could marry. The secular world talks of the division between Roman Catholic and Greek Orthodox as the 'Great Schism', but more often, when the Catholic Church talks of the 'Great Schism', it is the western schism of 1378-1418, in which various claimants vied for the power and wealth that came with the papacy. This western schism was called the 'Great Schism' in order to differentiate it from the several other papal schisms in the Catholic Church, with John W. O'Malley SJ saying in A History of the Popes, page 150 that the schism was certainly not the first papal schism, nor would it be the last.
The earliest Christian writings, from the epistles of St Paul and the apocryphal Gospel of Thomas demonstrate that the Christian Church has never been united. Differences over theology, such as the date of Easter or the providence of GThomas are arguably more noble than the disunity over power and access to the vast wealth of the Church.
Comment: Wow. Very detailed answer. It's interesting to note that some Christian denominations do value the so-called unity of the church, assuming that at one point, there was only one pristine early church which became corrupt. That's a point often made by Restorationists.
Comment: Assuming that your point is true and factual, Restorationists are definitely in the wrong.
Comment: @Anonymous Presumably by my point, you mean my references in the last paragraph. You will see that Paul several times referred to "false apostles" and "super apostles" who disagreed with his teachings - therefore disunity.  What we know of his theology (one example: the appearances of the risen Jesus) differs very much from the gospels accounts. The mere fact that GThomas is generally dated to the middle of the first century is further evidence of disunity, given that it is evidence of Gnostic teachings before even the first NT gospel (Mark) was written.
Comment: The fact that gospel of Thomas is not included in the Bible, I think, suggests that there was a major rejection of gnosticism in the early church, and somehow only non-gnostics got to decide what to include in their own biblical canons.
Comment: I am not aware of any major branch of Christianity that accepts the gospel of Thomas as an authoritative book of the Bible. It may have been a very early church division, and the non-gnostics somehow won over.
Comment: Yes. I make no suggestion that the Gnostic teachings were more true than those of what became the Catholic-Orthodox branch, but merely showed that divisions amongst Christians on matters of theology existed already by the middle of the first century.
Comment: The tricky thing is that, if the Gnostic teachings were truer, then Christians are probably screwed right now. But if the Gnostic teachings are truly false, however defined, then the "church division" would probably not be considered a church division at all, but rather, some people trying to hijack the truth.
Answer: Following the Julian Calendar which currently places the vernal equinox on April 3 is how it differs from western calculations.
You also have the 19 year metonic cycle used in the paschal tables devised millenia ago. I believe the Latins use a different mathematical cycle.
The thing about christian "unity" makes absolutely no sense in an Orthodox context as we dont include those outside our borders into the equation. Anyone can adopt the Nicene formula of the Alexandrian Paschalion if they so wish to but it has no bearing for the Orthodox.  And even then eikonomia (leniency) can be employed for unusual circumstances that a specific local church may face.
Answer: The Orthodox Church celebrates Pascha (Easter) on the first Sunday following the first full moon after Passover.  This naturally means that we, unlike others, never celebrate it before the annual Jewish holiday of Passover.
Comment: This answer would be stronger if you included a source that this is how the Orthodox calculate Easter, and that it is different from how Roman Catholics calculate it.
Comment: http://usa.greekreporter.com/2015/04/05/why-orthodox-christian-easter-is-later-than-the-catholic-one/
Comment: Good links.  If you could summarize them in your answer (and cite them appropriately), that'd be great.  Emphasizing the parts that are not already covered in Dick Harfield's answer would be great too.
Comment: Welcome to Christianity.SE. For a quick overview of what this site is about, please take the [Site Tour](http://christianity.stackexchange.com/tour). And for some tips on writing good answers here, please see: [What makes a good supported answer?](http://meta.christianity.stackexchange.com/questions/692/what-makes-a-good-supported-answer) I do hope you'll stick around!


How to seal a refrigerator water line

Question: I have a GE GSS22JEPDBB model fridge. The water line that goes into freezer door and then to the dispenser is leaking water right at the bottom of the door. Not sure exactly where. I suspect this is the source of the leak because it was damaged during a move. Unfortunately, I found out that I cannot replace this particular water tube, I would have to replace the entire door.
Is there any way to somehow seal the portion of the tube by gluing a seal as a 'wrapper' of sorts instead of shelling out $hundreds for a door? Any creative suggestions?
Comment: Does this answer your question? [How to replace GE water dispenser tube](https://diy.stackexchange.com/questions/192661/how-to-replace-ge-water-dispenser-tube)
Comment: Hey Jimmy. No unfortunately it doesn't. If I do cut the tube, how do I go about attaching another piece to it?
Comment: Hello, and welcome to Home Improvement. Please don't ask multiple questions on the same topic.
Comment: Thanks, Daniel. In retrospect, I should have updated the original question, which I've done now. I guess I posted a new one to get get an answer quickly as there was no activity on that post for a few days.
Answer: This is why you are not getting helpful answers:

"the dispenser is leaking water right at the bottom of the door. Not sure exactly where"

Without an idea about the source, location, and nature of the leak it is impossible for anyone to tell you how to fix it. Most assuredly, any attempt will fail unless you pinpoint the leak source.

How to seal a refrigerator water line


One of the students whose mobile _missing(is or are)

Question: Usage of "one of" if a relative pronoun whose is used in the sentence what will be the verb?

One of the students whose mobile (is/are) missing
Answer: Whatever the case, the verb relates to the mobile, not the students. So since the student is only missing one mobile, you would use the singular here.
Answer: What is missing in this sentence? Is it singular, or plural? If it is singular, then you need is missing, and if it is plural, you want are missing.
As you have written it, the thing that is missing is mobile, so you must have is missing.
Whether you should be saying mobile is or mobiles are is a whole other question, and one that I've definitely known native speakers to differ on. Personally, I'd make it mobiles are, because there is more than one mobile phone involved.
One of in this case doesn't change anything, because it's "one of (the students whose mobile is missing)". However, you could have:

One of the students' mobiles is missing

There you can see that one of causes an expression whose grammatical number is plural, "the students' mobiles" and makes it singular by indicating that the reference is to just one of them, "(one of (the students' mobiles)) is missing".
Answer:
One of the students [whose mobile is missing] is very upset.

Your example was just a noun phrase, so I've added the predicate "is very upset" to produce a complete sentence.
You've used singular "mobile" , so I'll assume that just one mobile is missing.
The one of x who construction often causes confusion since either singular or plural agreement is possible depending on the intended meaning.
Here, the natural interpretation is that it's not a matter of there being a set of students whose mobiles are missing, but of there being one student whose mobile is missing.
The relative clause thus belongs in the topmost noun phrase, not the one with "students" as head. Which means that the verb in the main clause and the one in the relative clause should be the singular "is", as shown.
Answer: The sentence is incomplete because you haven't finished talking about the main subject—the student. You actually need to have two verbs, each of which will be formed based on its own subject.
There are various possibilities, involving one or more students and there being one or more phones owned by those students:

One of the students [whose mobile was missing] was distraught.
One of the students [whose mobiles were missing] was distraught.
Two of the students [whose mobiles were missing] were distraught.

It's possible to describe a situation where all of the students had multiple missing phones, but the language becomes more complicated:

Two of the students, [each of whom whose mobiles were missing], were distraught.

The only way to make it clear that multiple phones belonged to every student is to use each, in order to make it clear that mobiles is being used for individuals.


What is the difference between source and destination sequence number in AODV?

Question: What is the difference between source sequence number and destination sequence number in RREQ packet in AODV?
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
Answer: According to my understanding, they are two different entities. They are completely independent of each other. A node's sequence number gets incremented either when it broadcasts a RREQ packet or when it is the destination node, before sending the RREP packet.


How to install Windows Web Services API (WWSAPI) in a Server w/o Internet Access

Question: I'm trying to use Visual Studio 2012 Remote Debugger in a Server with Windows Server 2008 R2 SP1 x64 located in a DMZ, in a Development Environment. This server doesn't access to the Internet directly but through a Firewall. So, I downloaded the Remote Tools for Visual Studio 2012 from my workstation, and copy it to the Server, install it and everything is ok.
Well, when I started the Remote Debugger Configuration Wizard, and it try to install the Windows Web Service API, it fails and shows the next message:

Failed to complete the Visual Studio Remote Debugger Configuration Wizard
The debugger was unable to install Windows Web Services API.
  Downloading the update installer failed. Please ensure that your
  computer is able to access the internet.
Download URL: http://go.microsoft.com/fwklink/?LinkId=215754
  Internal code: 0x800c0005
To close the wizard, click Finish.

So, because I'm a good boy, I press Finish to close the wizard. But before I go to the Download URL provided by the wizard, and has no success because it drive me to the Microsoft.com Search (http://search.microsoft.com/en-US/search.aspx).
But, I'm a man! I will not cry, and keep googling (searching?) but this time I was searching for WWSAPI Redistributable, but has no success at the time, then I search for a similar situation to mine here, and this is what I got Unable to install Windows Web Services API for Remote Debugging with VS2012, but doesn't has a solution, so I decided to ask at StackOverflow because, I'm almost desperate to find a solution for this. So, I hope you can help me to find a Solution to my situation. Thanks!
Comment: Could you please let us know what's your server OS version?
Comment: Windows Server 2008 R2 SP1 x64
Answer: Please refer to workaround described here, it solves this exact problem:
https://connect.microsoft.com/VisualStudio/feedback/details/763521/cannot-run-visual-studio-2012-remote-debugger-on-windows-server-2008-non-r2

Install Windows Live Essentials from the following link.
http://go.microsoft.com/fwlink/?LinkID=255474
One of the installed dependencies is the required Web Services API.

Also, please, sign in and vote for the bug solution, to give regard JustinPealing who worried first to open the bug, and who found this workaround


DXA development documents

Question: I just start to look into DXA Java version for a prototype project. I have been doing some google search but I could not find anything for development guide. I could setup and deploy the war to Tomcat server by followed this blog https://community.sdl.com/products-solutions/solutions/customer_experience_cloud/digital-experience/tridion/tridion-developer/b/weblog/archive/2015/12/15/getting-started-with-dxa-java
Could anyone share some links or documents for development?
I plan to use DXA Java version 1.3
Thanks
Answer: For development you can refer the official documentation link

DXA development documents


How tall was Frederick the Great of Prussia?

Question: Frederick's father, Frederick Wilhelm I of Prussia, was somewhat short at 5'3" (160 cm), as discussed in an article on the Potsdam Giants. But how tall was Frederick II?
Comment: Frederick I was Frederick II's grandfather. His father was [Frederick Wilhelm I](https://en.wikipedia.org/wiki/Frederick_William_I_of_Prussia).
Comment: thanks for pointing out - fixed!
Answer: Frederick the Great was rather short as well.
5'2"
The city of Potsdam would be one source for giving you that number:

FRIEDERISIKO. Friedrich der Große
Ausstellung der Stiftung preußische Schlösser und Gärten Berlin-Brandenburg | neues Palais und Park Sanssouci "Fünf Fuss, zwei Zoll" (PDF)

With is cited by Google's answer box as 1,62 m, via WDR: Stichtag
24. Januar 1712 - Friedrich II. von Preußen wird geboren (and repeated on Friedrich II. der Große (Preußen))

Other sources give a height of just ~1,60m:

Friedrich den Großen von Preußen "klein" zu finden, obwohl er nur um die 1,60 Meter

These may be a bit more complicated, as units of length weren't as standardised as today:

1 Dezimal-Fuß = 0,3766243 Meter (m)
1 Dezimal-Zoll = 0,03766243 Meter (m) (Das Königliche Magdeburger Maß von 1755 - 1816.)

Measures of length
With regard to the length measures, a distinction must be made between 3 different periods:

the Berlin measure between 1713 and 1773.
the Rhineland or also so-called Brandenburg measure between 1773 and 1816.
the Prussian measure after 1816.

WP: Alte Maße und Gewichte (Preußen)

1 Preußischer (Rheinländischer Fuß) = 0,313853497 m
1 Preußischer Zoll (1/12 Fuß) = 0,0261545 m (University Dresden, Architecture, Old units of length, PDF)

The first would give an incredible height, and not dezimal but duodezimal was more often in use. So the numbers for the latter would be
~ 1,6213 m
The minimum height requirement in his army (except for artillery) was exactly 5 feet.

When Frederick was fourteen he was appointed Major of the Potsdam Grenadiers, in other words the giants, and spent part of his time at Potsdam. A very small major he must have seemed; as a grown-up man he measured five feet seven; he was a particularly thin and peaky boy whose face seemed to contain only two enormous blue eyes…
— Nancy Mitford: "Frederick the Great", Hamish Hamilton: London,  1970.

With that number we arrive with a Prussian definition at 1,75 m;
we arrive with modern definition of length at 1,7 m.
No German language source I found corroborated this measurement of 5'7", Mitofrd doesn't give a source, and I strongly suspect some kind of conversion error in Mitford's biography.
In contrast, a nicely sourced reference gives the following:

Frederick the Great was in fact, according to his contemporaries, "somewhat below medium height", just five feet two inches, a maximum of five feet five inches, i.e. about 1.64 metres long. He was considered "petit" by his contemporaries even in the 18th century, when people were not as long on average as they are today.
— Wilhelm Bringmann: "Friedrich der Große. Ein Porträt", Herbert Utz Verlag: München, 2006. (Interestingly, also quoting Mitford, with 1.64 m, plus another source 'Vehse'. Alas, the snippet available now doesn't include the complete bibliography: PDF)

Example for a source quote in French and German attesting his petit physique:

Which gives us actually two different numbers for heights, one with suspicous exactness relating to when he was 19: 5 feet 2 inches and 3 lines. The other then contrasts this seemingly over-exact number without an actual source for it to the same measurements in feet and inch that is reported for Napoleon. But the latter height description for Frederick is then 5'5" (no lines) alleged by his last servant, shortly before his death:

What then follows is a description delivered by a  French diplomat.

— Johann David Erdmann Preuss:  "Friedrich der Grosse: Eine Lebensgeschichte", Band 1, p20, p 420. (Albeit the latter, lets call it 'rare' measurement, this author already acknowledges the servant source as "imprecise" with "5 feet 5 inch".
Note also the picture included here of Frederick's death mask. And keep in mind that the description of his nose in this written source from 1832 indicates that a certain hagiographic embellishment is certain in that source that also fails to specify which 'foot' it uses, and simply glosses over its own French source material being in conflict with itself,  the French calling out a 'petit' man, while his biographer describes him 'of average height'. In any case, it is rather unlikely that the king continued to grow that much above his father after being a known smallish boy and later in old age walking standing rather bowed down.
(Cf: — Bernd Krysmanski: "Nur Hogarth zeigt den Alten Fritz wahrheitsgemäß mit krummem "Zinken". Die uns vertrauten Bilder von Pesne bis Menzel tun dies nicht", in: Effinger et al. (eds.): Von analogen und digitalen Zugängen zur Kunst – Festschrift für Hubertus Kohle zum 60. Geburtstag, Heidelberg: arthistoricum.net, Advance online publication, 07.06.2019, https://doi.org/10.11588/arthistoricum.493.c6566)
Comment: With your edit, you've already done plenty here so need for another answer I think. +1
Comment: This seems to be disputed, and Nancy Mitford's 1970 biography of Frederick the Great gives his height as 5' 7'' (or 170 cm).
Comment: @LarsBosteen The Mitford ref is a ref, but one that I would doubt *quite* a bit (as explained). What is the source for 'seems to be *disputed"*? I'd like to weigh those arguments (unless you want your own A here ;) but cannot see any 'dispute'…
Comment: @LarBosteen German sources use 5' 2" (Due) Prussian Feet, which is just under 5' 4" english feet. 1.6215764 meters when using the legal meter (139.13/443.296).
Comment: @MarkJohnson - Interestingly, Napoleon was *also* quoted at 5'2", but when adjusted from French to English feet that works out to more like 5'5". So Frederick was actually shorter than Napoleon (but at the time this was barely below male average, so that doesn't mean much).
Answer: At the age of 19, Friedrich the Great was

5' 2" 3/12 (Prussian (Duo) Feet) = 1.6281150157 (legal) meters

accourding to literature published in 1832.

Note:
There are 2 values used for calculations from Prussian (Duo) Feet to meters

legal: where the value for amount of Paris Lines per meter has been rounded

0.3138534974=(139.13/443.296)

exact: used for mathematical calculations

0.3138535427=(139.13/443.295936)

Sources:

1832: Friedrich der Große: eine Lebensgeschichte - Johann D. E. Preuss - Google Books

Page 39

Frankfurter Geschäfts-Handbuch, 1845

Page 69, 185


What if I won't sign the contract immediately?

Question: I was in an interview and I'm pretty confident I will get the job. I'm wondering one thing. If they asks me to come to the office to sign the employment contract, what will they react if I say that I can take the contract and show it to a good friend of mine, who has studied law, before I sign it. Is this wise? May I lose the job if I do like this?
Comment: If they refused you a job because you wanted to read the contract, would you really want to work for them anyway?
Comment: "what will they react if I say that I can take the contract and show it to a good friend of mine, who has studied law, before I sign it" - Do you plan on phrasing it exactly like that, or will you instead say something like "I'd like a day or two to read over the contract before signing it."?
Answer:
Is this wise?

Reading the contract before signing it is definitely a wise idea, and showing it to someone with more expertisey is, likewise. In fact, most companies will send you the contract a few days before the signing specifically so you have time to read it before you sign it.

May I lose the job if I do like this?

Yeah, but you really don't want to work for a company that wants you to sign a legally binding contract without reading it first, so if that happens, consider it a bullet dodged. There are no good reasons to not let a new employee review the contract before signing, only nefarious ones.
Comment: That is pretty much it. Guess what, I do not show my contracts to a friend who studied law. I inform anyone that I show them to my lawyers - 3 different, working for different companies. It is SOP - Standard Operating Procedure. Do not like that? Well, here goes the contract - into the shredder.
Answer:
Yes, it's a good idea, but you should execute this carefully
Let them know up front that you would like some time to study the contract and any other agreements you are supposed to sign (confidentiality, IP protection, code of conduct, etc).
If you get push back, reply with something like "Surely you value employees that are thorough and apply due diligence to important decision. If I had to sign a contract on the company's behalf, would you want me to do so without reading it first ?"
Do NOT tell them that you are going to show it to your friend. These contracts are often considered confidential by the employer
Answer: Every company I have ever dealt with gives sometime for the person to evaluate the offer. I have seen them as short as a few days, but up to a week isn't unusual.
I suppose if the the job was an internal transfer/promotion the deadline would be very short because the benefits wouldn't be changing, but pay, location, and title would be.
A proposal that has a deadline of less than a day doesn't leave anytime for questions.
You wouldn't buy a used car without having the opportunity to inspect it, and test drive it; therefore  asking you to sign a contract without time to review it would also not be advisable.


Accessing joined Image using ee.Join.saveFirst() in Google Earth Engine?

Question: I am trying to append a band from a scene in one Landsat 8 image collection to a scene in another Landsat 8 image collection in Google Earth Engine. I am joining the scenes using ee.Join.saveFirst()
The join works and I am able to see the joined scene in the image properties, however, I am not able to access the band.
The resulting image collection behaves differently than a normal image collection.
If I try to map a function (even where input equals output) on the collection, the resulting image collection doesn't know it bands anymore. Applying a reducer doesn't work at all.
Has anyone experienced similar issues and knows a sollution?
Here my code:
function addMask(img){

  // grabbing the attached image
  var fmask_img = img.get('fmask');

  // Trying to access a band in the original image works
  //var b1 = img.select(["B1"]);

  // Trying to access a band in the image doesn't work
  //var fmask = fmask_img.select(["fmask"]);

  //trying to add a band from the attached image to the orignal image doesn't work
  //var newImg = img.addBands(fmask_img, ["fmask"])

  //trying to all bands from the attached image to the orignal image also doesn't work
  //var newImg = img.addBands(fmask_img, ["fmask"])

  //even trying to the origianl image to is self doesn't work
  //var newImg = img.addBands(img)

  return img // returning the unchanged image instead of newImg
}

// Load a primary collection: Landsat imagery.
var primary = ee.ImageCollection('LC8_L1T')
    .filterDate('2014-04-01', '2014-06-01')
    .filterBounds(ee.Geometry.Point(-122.092, 37.42));

// Load a secondary collection: MODIS imagery.
var secondary = ee.ImageCollection('LANDSAT/LC8_L1T_TOA_FMASK')
    .filterDate('2014-04-01', '2014-06-01')
    .filterBounds(ee.Geometry.Point(-122.092, 37.42));

// Create a filter to define a match based on the scene ID.
var sceneFilter = ee.Filter.equals({
  leftField: "LANDSAT_SCENE_ID",
  rightField: "LANDSAT_SCENE_ID"
  })

// Define the join.
var saveFirstJoin = ee.Join.saveFirst({
  matchKey: 'fmask',
  ordering: 'system:time_start',
  ascending: true
});

// Apply the join.
// This returns an image collection
var landsatFmask = saveFirstJoin.apply(primary, secondary, sceneFilter);

// Mapping a simple function where input = output returns an image collection
var fmask = landsatFmask.map(addMask);

// applying a reducer on the orignal collection works
var primary_median = primary.median()

//applying a reducer on the orignalnew collection works doesn't work
//var fmask_median = fmask.median()
//var joined_median = landsatFmask.median()

// Display the result.
// the orginal collection
print('raw:', primary)
// looks the same as the orginal, only difference is that images inside the collection have an additional property "fmask" with the joined image inside
print('Join.saveAll:', landsatFmask);
// looks the same as the joined collection, but now the band list of the images collection is empty ??
print('fmask:', fmask);

Answer: ok, after playing around with it a bit more it turns out I need to type cast my images in the function
function addMask(img){

  // cast the input image
  var i = ee.Image(img);
  // grabbing the attached image and cast it as well
  var fmask_img = ee.Image(img.get('fmask'));

  //now i can add the band
  var newImg = i.addBands(fmask_img, ["fmask"])

  return newImg
}


How to swap displays in OSX

Question: I have a Macbook Pro running Lion and an external monitor.  I use dual displays.  Is there anyway I can easily switch the displays?  For instance if I have Safari open and sitting in my laptop screen and QuickTime running on the external monitor is there any thing that would allow me to push and a button and switch the displays so that QuickTime is in the laptop  screen and Safari is in the external monitor?
Answer: Use mission controller. By default swipe up with 3 fingers (on trackpad).
Then click and drag safari to desktop 2. From now onwards whenever you start safari it opens on external monitor (only when it is connected).
Hope this helps.

How to swap displays in OSX


Make an area transparent through all the layers in gimp

Question: I have an image created by a graphic designer and it has about 20 layers in it. How can I make an area transparent all the way through so that wen I export the image to PNG it will have a transparent "hole" in it?
Answer: You could apply an identical layer mask to each of the layers.  Make one layer mask, copy it, paste it, and anchor it into another layer mask, 20 times.
You could hide the background layer (if there is one), and merge the visible layers to one layer, then add one layer mask - since it's being output to a png anyway, which has no support for layers.
You could hide the background layer (if there is one), then create one new layer from visible, and add one layer mask to it. Then hide all the other layers.
Answer: The Quick And Dirty Way

Right click any layer in the layers dialog.
Click Flatten Image (the last option in the right click menu).
Optional:

Right click the resulting layer.
Click Add Alpha Channel.

Use the eraser or selection tool to create the hole.
Export.
Comment: Maybe... I assumed that wouldn't be a problem, since the OP only seemed to care about the exported PNG (quote: »wen I export the image to PNG«).
Comment: Why the downvote? A small comment with a justification would be nice.
Comment: Your approach kills the layers (even if only temporary), and people think this is not what the question is about?
Answer: Use the clear-layers script.

clear-layers deletes the selection in several layers. Edit/Clear layers/All affects all layers, while Edit/Clear layers/Visible only affects visible layers.

You can also do it directly in the python-fu console (warning, this assumes that there is only one image loaded in Gimp):
image=gimp.image_list()[0]
for layer in image.layers:pdb.gimp_edit_clear(layer)

(Strike enter twice after the second line.)
Answer: on gimp 2.10.30
create a top transparent layer and set it to "erase mode".
now, draw on the erase layer with any color.
and make it sure all layers below it have the alpha channel.
obs.: you can set the opacity of the erase layer too.


How to create unique 3d star maps?

Question: I have been trying to create a calculator which finds the distance between two stars that the user chooses. But I'm having a hard time visualizing where these stars are in real space. Do you know of any software that could actually help me crate a star map with only the stars in my calculator? I know of some star maps like Celestia, but I would like to be able to create my own map that only contains certain stars. If there isn't anything, I can find my own solution. Thanks in advance for any answers!
Answer: I hope the following doesn't come across as self-promotion, but you can have a look at the source code for my near-space 3D map:
http://beyondproxima.com/
Just View Page Source.
It's not perfect - the 3D projection is not geometrically accurate, and some brighter stars are duplicated. But it might give you a starting point?
Answer: If you don't mind doing a bit of math and/or some light programming, it's not all that hard.
The position of stars is defined by declination and right ascension and, of course distance.
Declination is basically just North/South.   Polaris, for example has a declination of +90 degrees (well, pretty close).
Stars directly over the equator, declination is 0.  Above the south pole, -90.
Right ascension is measured in hours, minutes and seconds, where each hour is 15 degrees of arc.  (24 hours, 360 degrees - that makes sense, right?)
If you want to create a cartesian map, set Earth (or the Sun, 1 AU won't change things much) at 0,0,0.   I personally find using East-West and Up-Down a little confusing (on Earth we use, East-West, North-South and Up-Down for 3 dimensions), but in space, I use North-South (X coordinate), and unnamed Y coordinate and Z coordinate when converting to cartesian, but you can use whatever terms you like as long as yours are consistent.
1 light year at 90 declination would be 1,0,0.     1 light year at -90 declination would be -1,0,0.     With 3 cartesian coordinates you can work out the distance between two stars easily, just use a little 3D Pythagorean Theorem.   Subtract the variation in each coordinate square them, add the and take the square root.
Using Alpha Centauri as an example:
Right ascension 14h 39m 36.49400s
Declination –60° 50′ 02.3737″
Distance 4.37 ly
For the North-South direction, take the sine of the declination and multiply by the distance.     Sine of -60 degrees, 50 minutes and change is about -0.873, giving Alpha Centauri (A or B, take your pick) a -3.816 North/South coordinate and a remaining 2.13 light years for the other two coordinates.
Now convert the 14 hours 39.6 minutes into degrees, 15 degrees per hour, and you get 219.9 degrees. Take the sine and cosine of that number and multiply by the remaining 2.13 light years for those two coordinates and you get -1.366 and -1.634, so Alpha Centauri (they're close enough that it doesn't matter which) has the cartesian coordinates, in light years of -3.816, -1.366 and -1.634 relative to the sun.
Set up a little program and you can plug in declination, right ascension and distance for any star and you can convert their position to cartesian coordinates.   There may be easier ways to do it or programs already set up or 3D graph software, that allows you to plug in the polar coordinates directly, so there may be easier methods, but that's the method I know to create a local star map, if desired.
You can also look up local star maps easily enough to check your work, but it's difficult to display 3 dimensions on a 2D screen, so it can be hard to eyeball distances from a local star map.
Wikipedia local star map
Similar map
Keep in mind, for more distant stars, distance becomes harder to measure, so the further away you go, the less accurate your map will be.  Betelgeuse, for example, has a pretty big range of uncertainty on it's distance. Big enough that measuring the distance between stars that far becomes an exercise in futility.
Comment: I dont think you understand, I already know the coordinates, I just want to know of a 3d graphing software I can use to visualize the coordinates.

How to create unique 3d star maps?


Chandelier with candles

Question: I want to make a hanging chandelier with candles.
The centerpiece is Technic Knob Cog .
My initial thought was to design it just like the Big Ben Church bells (step 278).
However, I don't think that technic pin with bar extension will interface correctly with the technic knob cog as I think it needs an axle to hold it right? So I guess I need a way to hang a short vertical axle from a very long horizontal axle (or set of connected horizontal axles).
Answer: I'll confess - my inspiration for that element in my answer to your 4 candles question came from set 10273 - Haunted House which uses it for exactly that purpose - instructions are here (180MB), it's on page 119:

It uses a Technic, Axle 5 with stop to hold the knob cog up, and it's inserted into a Technic, Axle and Pin Connector Angled #1 that's hanging from a beam made from Axle Connectors 2L (Smooth) and Axle 2 Notched.
Comment: Good gravy, 180 MB for LEGO instructions? Wow. Thanks for noting that
Comment: Yeah, it's one big book. I thought I ought to call it out ;)
Answer: I just realized you can put an axle through the 180 degree connectors just like you can a technic pin. Then, you just need a bush or something above the vertical axle to hold it in place.

Chandelier with candles


Where to create SQL databases online?

Question: I am wanting to create my own online SQL database for a website that is going to feature some interactive r shiny/plotly apps. I see that there a appear to be a few options through things like amazon web services and microsoft. Does anyone have any recommendations for something that would be free and minimal work?
Answer: I can recommend you to try AWS and/or Google Compute Engine.
AWS has free tier plans that include everything an operating system can do, but the free tier plan is limited both in time and functinality.
Gearhost also offers free plans that include a database, but the offer is limited. It can make a large difference if you only pay $5 monthly, then you'll be able to use more advnced option more suitable for production.
If your project is not for production and only development, you can go with the free tier plans.
Answer: AWS may be good to get your feet wet, but once your free trial is up, it is MUCH more expensive than Linode.com for the resources you can get.
Additionally, with Linode, you have complete and total control of your VPS - what Linux (or BSD) distribution you run, you are the root user, you are in control of all of it.
Linode.com is $5/mo for the cheapest "machine" you can up or down size on the fly at any time, they do hourly billing or by the month, great company to work with, been a happy customer for 12+ years.
When you sign up, use promo code DOCS10 for a $10 credit.

Where to create SQL databases online?


Tall, quick growing privacy tree species

Question: Can someone recommend a tall, quick growing tree that's not overly invasive that would serve well to plant around a backyard to help break the line of sight of neighbors into my pool / backyard?
Comment: This is going to vary widely by region - you'll almost certainly get the best answers from your state forestry service or agricultural extension.
Comment: +1 to that, good call. I'm in midwest US, will ask around to some local arborist or something.
Comment: How much shade, sun? How much room width and length will you have for the plants? A picture of the swimming pool view and the area you want to plant.  Have you thought of building an arbor or architectural screens?
Comment: I'm a Landscape Architect...could you get graph paper, whatever scale that works and make a plan showing: 1. Property lines of your property and your neighbors; 2. Placement of your home and their home.  Your swimming pool, any fencing, existing plants. Label views from your home.  For example; dining room view, upper story bedroom view...utilities. Send photos of the different views. Let's see if we can communicate using a scaled base plan in bird's eye view...oh, and include North, prevailing winds, scale, elevations (height) and any interesting notes. Include your ideas!
Answer: Try a beech hedge. The leaves stay over the winter (they go brown and are rather pretty) and they go rights down to the ground. Trim it at the top to the height you want.
Answer: Not sure if Palm trees grow in your area. Palm trees grow quickly and are very bushy. they work as a good curtain.
Answer: Where I used to live everyone did Leyland Cypress.  The are fast but not as dense when young as I would have liked.  I found Thuya plicata 'virescens'. They provided screening instantly at 8'.  They are a variety of our Western Cedar that grows more narrow and yet very dense, very dark green.  They are much better in the wind than the Leyland oddly enough. In 5 years they were 15' and 5' to 7' wide some as close as 5-6' apart.  I never had to shear them and they stayed dense to the ground.
Try not doing a straight line.  I like to offset them from each other, grouping them in a more natural-looking way.  If one dies, no one will be the wiser.  I even like getting a few smaller trees to mix as well as a few understory, deciduous trees such as Serviceberry or Elderberry (the dark purple was gorgeous)! Birds loved these trees. Don't stake your trees if you can possibly help it.  They will grow faster and stronger if you don't stake them. Try to dig up the whole bed you will be using for plants.  If you are removing grass for this bed use it to form the foundation of your bed just stack the chunks upside down and top with 6-8" or more of good topsoil.  Plan it so that the rootballs of your plants sit on undisturbed soil and keep soil away from the bark of the tree.
Answer: Thuja "Green Giant," worked for us. It grew about a foot a year and blocked out the neighbors really quickly. Although it does grow REALLY tall.
https://www.youtube.com/watch?v=qaHrOYx1w4M


Tika and Solr Drupal 7 Indexing on Cron

Question: Using Drupal/Search API module/Solr/Tika we are trying to index a large number of files.
I've set up the index and everything works fine until I include the Search API attachments module.
When we run cron, tika is not being called. We know this because we put in a snippet of PHP code to write to the system log at the end of the tika module and that message never shows up. It does show up when running the index manually.
Additionally, the number of items index does not go up after a cron run.
We also noticed that if we run tika from the command line we get the following error at the top of the output:
INFO - unsupported/disabled operation: EI
The index works as expected without checking the box to index attachments both on cron and by manually indexing.
Any idea what the problem might be?
Thanks!
Site Built On:

Drupal 7

Modules In Question:

Search API
Search API Attachments

Indexing with:

Apache Solr

Indexing Attachments using:

Tika Library
Answer: I have the same problem. But it does not seem to be a problem at all, because the document seems to get indexed anyway.
I guess it is a Tika problem, because some documents (pdf) are working well, others not. Maybe it depends on the pdf version. Try something more simple. I.E. I wrote a sample text and used the print to pdf function on my mac to get a simple pdf document. Or use a Word doc. We also had to apply the real-path patch to get Tika working with the files ... and the transliteration module to have clean filenames. For debugging search_api I use dd()-function from devel. In search_api_solr/includes/solr_httptransport.inc performHttpRequest() I call
dd($url); dd($options); right before $response = drupal_http_request($url, $options); (line:92) ... hopefully this helps.

Tika and Solr Drupal 7 Indexing on Cron


File manager issues since upgrade to 2.6.1

Question: I recently upgraded to 2.6.1 and i have had a few buggy issues in file manager since. Firstly i get a white screen of death on file sync and also when i click on a image link in the file manager table the light box is gone and it opens the image in the browser.
Thanks for any help
Comment: You may have a corrupt file in your themes folder. Can you download EE again and re-upload the themes folder. Backup your current themes folder first (especially for third_party and site_themes).
Answer: Turns out it was caused by Generate HTTP Page Headers being set as on in output and debugging.
This caused a real delay in the full page load and this caused the issues file manager.Turning it off and this sorted my problems


Why do I get a much better price for options with a limit order than the ask price?

Question: When I'm buying an option, I notice that if I set a limit order for in between the ask and bid - say half way, I can often get the option at that price. Why is it that way?  I thought the ask price was supposed to be the lowest that anybody was willing to sell it.
Comment: There is a lot of liquidity that is intentionally not broadcast to the public.
Comment: So you're saying, ASK is 30, BID is 20, you set a limit offer of 25, and get a taker at that price?  Sounds like a market maker, or someone else's opposing limit order?
Comment: The sample scenario you set up is correct.  I would naturally guess it's someone else's limit order - but shouldn't that be shown as ask price?
Comment: Yeah, I think you're right - the limit order would be reflected in the price, if it's a limit order submitted to the exchange anyway (as opposed to in software where the software paid attention to the bid/ask and submitted an order when it reached a certain point).  Edited my answer to reflect that.
Answer: Sounds to me like you're describing just how it should work.  Ask is at 30, Bid is at 20; you offer a new bid at 25.  Either:

A market maker fulfills your order
A new entrant matches your offer

Depending on liquidity, one or the other may be more likely.
This Investorplace article on the subject describes what you're seeing, and recommends the strategy you're describing precisely.

Instead of a market order, take advantage of the fact that the options world truly is a marketplace — one where you can possibly get a better price just by asking. How does that work? If you use a limit order (instead of a market order) when opening a position, you can tell your broker how much you are willing to pay to enter a trade.
For example, if you enter a limit price of $1.15, you can see whether the market-maker will bite. You will be surprised at how many times you will get your price (i.e., $1.15) instead of the ask price of $1.30.
If your order at $1.15 is not filled after a few minutes, you can modify your order and pay the ask price by entering a market order or limit order at the ask price (that is, you can tell your broker to pay no more than $1.30).
Comment: So my followup question would be this: if the market maker's real limit is below the ask price, why doesn't he just post that as his ask price?  I suppose the answer is that he wants to get unknowing people who make market orders to pay the higher price.
Comment: The market maker sees _your_ limit order, and chooses to fulfill it.  That's its job, not to post bid/asks.
Answer: There are people whose strategy revolves around putting orders at the bid and ask and making money off people who cross the spread.  If you put an order in between the current bid/ask, people running that type of strategy will usually pick it off, viewing it as a discount to the orders that they already have on the bid/ask.  Often these people are trading by computer, so your limit order may get hit so quickly that it appears instantaneous to you.  In reality, you were probably hit by a limit order placed specifically to fill against yours.
Answer: There are usually so many different options around for the same stock that some are rarely traded. Especially if the price has moved since the option was issued, nobody might be interested in that particular option at that price anymore. So the asking price might be something that someone asked for ages ago and that is much higher than anyone would reasonably pay today.
With a bid of $20 and an ask of $30, nobody is trading, but the value of that option is somewhere between $20 and $30. If the value is below $25, someone will notice your $25 bid and sell.
Answer:
I can often get the option at [a] price [between bid and ask]

The keyword you use here is quite relevant: often. More realistically, it's going to be sometimes.
And that's just how supply and demand should work.
The ask is where you know you can buy right away. If you don't wanna buy at ask, you can try and put a higher bid but you can only hope someone will take it before the price moves. If prices are moving up fast, you will have missed a chance if you gambled mid-spread.
Having said that, the larger the spread is, the more you should work with limits mid-spread. You don't want to just take ask or bid with illiquid options. Make a calculation of the true value of the option (i.e. using the Black Scholes Model), then set your bid around there. Of course, if not only the option but also the underlying is illiquid, this all gets even more difficult.
Answer: What you have to remember is that Options are derivatives of another asset like stocks for example.
The price of the Option is derived from the price of the underlying. If the underlying is a stock for example, as the price of the stock moves up and down during the trading day, so will the Market Maker's fair value for the Option.
As Options are usually less liquid than the underlying stock, Market Makers are usually more active in 'Providing a Market' with Options. Thus if you place a limit order half way between the current Bid and Ask and the underlying stock price moves towards your limit order, the Market Maker will do their job and 'Provide a Market' at that price, thus executing your order.
Answer: 1. To provide room for variation in the price of the underlying
Option prices vary based on the price of the underlying stock.
As a result, if the price of the underlying stock moves, the market maker posting option prices in the market has to adjust the price of his quotes to respond.  It can take some time to update each one, so often the market maker prices in a little 'buffer' so that his quotes are still valid if the market moves a little bit.
As a result these same market makers may 'hit' bids or offers at more competitive prices.
2. Willingness of market participant to buy options at the displayed price.
If people are willing to buy at the displayed price anyway, why improve upon it?
3. Payment for order flow
One practice that continues to this day is "payment for order flow" (sometimes called "customer priority").
A market maker can make an arrangement with a broker or an "order flow provider" (someone who aggregates orders from brokers) to have them 'direct' the order to them in exchange for paying the order flow provider a fee.  This fee allows them to gain market share without having to compete on price.
4. Penny Pricing
Most US stock options are priced in nickel ($0.05) increments.  However a few exchanges (BATS Options and NASAQ Options) operate order books that allow options to be priced in penny increments.  Those prices are not published on the market data feeds.  There has been some resistance against this (penny pricing limits how much money can be paid to an order flow provider).  Incidentally, these exchanges do not operate payment-for-order flow schemes.


Send email after 100 webform submissions

Question: I'd like to be able to send an email to the nth person (or every n people) that submit a specific webform. I've tried utilizing rules for this, but I can't seem to expose webform submission data to rules (using submission id). Any thoughts on how this could work through rules? Any suggestions for alternatives?
Comment: if you are able to code it by your self, i could give you an algorithm
Comment: I'm not very great with hooks but I can give it a shot. I'd figure I would just take the modulus of the submission ID, like: if(sid%n = 0)...Not sure if that is the best way to solve this or not.
Answer: Have you tried using Webform Rules ?
This should expose webform results to rules, then create a new rule with conditions "if submission ID is 100, 200 etc" then... action: Send email.
You would either need a way to find the nth of 100, or depending on how many submissions you are expecting, just check against a comma separated list, eg "100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200" etc
Comment: I do have webform rules enabled, but I cannot seem to find anything allowing me to access the submission ID. The rule is set up to fire after a webform has been submitted, but any sort of condition I put in doesn't allow for the submission ID to be accessed.
Comment: Sometimes to use the results of a field when using entities, you have to first use a condition "Entity has field" and then select the field you want to use.  There may be something similar with Webform Rules?
Comment: Unfortunately, I wasn't able to get any of the tokens to show up even after adding a field via "Entity has field". I'm able to do data comparison on the data of the submission (through the [data] token), but I'm unable to access any of the specific options of [data] (like [data:sid]).
Answer: in hook_webform_submission() there is a variable $submission. So all you need to do is to implement this hook in your custom module and check for $submission->sid accordingly to your wisches.
If condition matches: drupal_mail()
Answer: Use rules to add +1 to an integer field on a solitary node when a web form is submitted. Have another rule that fires when a webform is submitted and that integer field is equal to 100.
Use that rule to send an email and reset the integer to 0.


Are Q&As allowed that specifically point to the use of a particular product or service?

Question: So for instance if I have created a really great product for Ubuntu which is fully free and in my PPA, and my product would help a lot of people, would it be considered promotional spam if I were to post a Q&A where I ask a question, and then provide my product as the solution? Or would that by looked upon badly?
Comment: Don't leave us hanging in a vacuum, tell us what it is so we can make an informed opinion!
Comment: related: http://meta.askubuntu.com/questions/13715/should-i-keep-an-eye-on-spam-like-answers-about-free-software-or-why-do-people
Answer: Speaking generally, if...

It's relevant; it answers the question(s), and
You disclose your interest, and
You don't plaster the site with it...

... We have no problem with it. If somebody has a useful and helpful thing to share with us, I think we can accept that sometimes the people posting it might occasionally have a vested interest in that.
I'd look much less favourably on something —and someone— if they set up a question just to answer it with their product. While self-answering is generally seen as fine, you stretch its external usefulness when you start doing it to promote your own stuff.
And we start handing out suspensions like free candy if you start doing that from different accounts. AstroTurfing is toxic. Recommendations must be based on personal views.
If you suspect anything of falling foul of these guidelines, flag it up and we'll have a look.
Comment: So what if lots of people were having a problem, but there was no real fix for the problem, so I posted a question asking directly about that problem (as nobody else had already), where I answered with my solution, which may have been a link to my PPA which an explanation of use of the software etc to fix the problem?