Python classmethods: what's the difference between a member of an instance and a member of the class?
Difference between staticmethod and classmethod
How to prove that exponential grows faster than polynomial? Consider the following figure from Faraway's Linear Models with R (2005, p. 59).    The first plot seems to indicate that the residuals and the fitted values are uncorrelated, as they should be in a homoscedastic linear model with normally distributed errors. Therefore, the second and third plots, which seem to indicate dependency between the residuals and the fitted values, suggest a different model.  But why does the second plot suggest, as Faraway notes, a heteroscedastic linear model, while the third plot suggest a non-linear model?  The second plot seems to indicate that the absolute value of the residuals is strongly positively correlated with the fitted values, whereas no such trend is evident in the third plot. So if it were the case that, theoretically speaking, in a heteroscedastic linear model with normally distributed errors  $$ \mbox{Cor}\left(\mathbf{e},\hat{\mathbf{y}}\right) = \left[\begin{array}{ccc}1 &amp; \cdots &amp; 1 \\ \vdots &amp; \ddots &amp; \vdots \\ 1 &amp; \cdots &amp; 1\end{array}\right] $$  (where the expression on the left is the variance-covariance matrix between the residuals and the fitted values) this would explain why the second and third plots agree with Faraway's interpretations.  But is this the case? If not, how else can Faraway's interpretations of the second and third plots be justified? Also, why does the third plot necessarily indicate non-linearity? Isn't it possible that it is linear, but that the errors are either not normally distributed, or else that they are normally distributed, but do not center around zero? I would like to install Office 2015/365 on Ubuntu 15.04. I tried to install Office using Wine, but that did not work. Please note that I do not want virtualisation unless it has a -like behaviour, where application windows are treated like regular Ubuntu application windows by the system. Learn QM algebraic formulations and interpretations I have a good undergrad knowledge of quantum mechanics, and I'm interesting in reading up more about interpretation and in particular things related to how QM emerges algebraically from some reasonable real world assumptions. However I want to avoid the meticulous maths style and rather read something more meant for physicists (where rigorous proofs aren't needed and things are well-behaved ;) ) I.e. I'd prefer more intuitive resources as opposed to the rigorous texts.       Can you recommend some reading to get started? Lightning force:createRecord capture redirect after save Is there a way to use force:createRecord but capture the redirect to the newly created record page that occurs after saving the record? Finally, prevent the redirect from completing?  createRecord : function (component) {     var createRecordEvent = $A.get("e.force:createRecord");     createRecordEvent.setParams({         "entityApiName": "Event__c"     });     createRecordEvent.fire(); } The recent question  made me realize that I don't have any understanding of why one would upload to a preprint site.  (I don't work in a field where they seem to be common.)  Why would one be concerned about getting a manuscript on arXiv, if it's already under review with a journal?   Is it because of the long publishing timeline of journals?  (That could explain why computer science &mdash; which publishes much more in conferences &mdash; doesn't seem to do much with them.) What's the analogue to spherical coordinates in $n$-dimensions? For example, for $n=2$ the analogue are polar coordinates $r,\theta$, which are related to the Cartesian coordinates $x_1,x_2$ by  $$x_1=r \cos  \theta$$ $$x_2=r \sin  \theta$$  For $n=3$, the analogue would be the ordinary spherical coordinates $r,\theta ,\varphi$, related to the Cartesian coordinates $x_1,x_2,x_3$ by  $$x_1=r \sin  \theta  \cos  \varphi$$ $$x_2=r \sin  \theta  \sin  \varphi$$ $$x_3=r \cos  \theta$$  So these are my questions: Is there an analogue, or several, to spherical coordinates in $n$-dimensions for $n&gt;3$? If there are such analogues, what are they and how are they related to the Cartesian coordinates? Thanks. Merging two arrays in .NET Is there a built in function in .NET 2.0 that will take two arrays and merge them into one array?  The arrays are both of the same type. I'm getting these arrays from a widely used function within my code base and can't modify the function to return the data in a different format.  I'm looking to avoid writing my own function to accomplish this if possible. Can we implement a dead time on answers for high reputation user Summary: High reputation users on SO come swooping in the second a simple question is posted, and get the first answer in before I've even opened my Python interpreter to test my idea out.  This actually is a problem because it prevents use lower users who aren't as good  at programming from getting any answers in.  This makes it very hard to build up reputation.  Thus, I propose a short dead time for high reputation users where their answers do not appear.  The Problem: This isn't just reputation.  By answering questions and having discussions with OP, we all get better at our language.  Teaching is one of the best ways of learning, and a more well versed population is absolutely good for SO.  (If anyone wants to argue that, go home)  While its nice to have folks who can quickly answer nearly all questions in a jiffy, its a little frustrating for those of use who simply aren't as fast, but still want to contribute.  The result is that many people do not answer questions because they feel like they just can't get an edge in.  SO should aim to incentivize as many answers by as many users as possible.  The most answers from the most users is the most beneficial situation for the site and the community. Once we accept this idea, it is clear that something needs to be done to address the issue at hand    The Solution: Luckily, this is an easy problem to solve; we use a dead time.  High reputation users can post answers whenever they like, but they won't appear until after the dead time is completed.  The trick is balance, a dead time which is too long will harm the OP as the question will remain unanswered, however, a dead time which is too short won't actually fix the problem.  There definitely needs to be a discussion about what "high reputation" means and what dead time to use, but it should be independent of whether y'all agree that this is a problem.  So, what do you think?  EDIT: Wow, -18, I leave for lunch for 30 minutes and this is what happens!  I guess y'all think this is a bad idea, but let me try to clarify a few things on which I was unclear earlier.  This is not about reputation.  This is not about getting the first answer just for the sake of getting to say "in before..."  This is about learning.  By getting a shot at answering questions before the high reputation users, people learn. Think of it as doing an example problem in class before the teacher does it. You get a chance to try it yourself, test your knowledge, and if you fail, then the teacher is right behind you to show the correct solution.  This is what I'm trying to accomplish. However, seeing the solution, and then trying to answer the question, is not very helpful. This is how I view the status quo.    In response to Mr. Pieters' answer and comments: You're absolutely right, this is not about quantity, its about quality.  The fastest answer isn't always the best.  But asking the high reputation users to take a step back for a few minutes is a means of getting there.    Hopefully this clears things up a bit. How to test for an hold item name in Minecraft? I'm trying to make a command block that spawns an item in front of you if you are holding an item with a specific name. I've got these two working scripts;  /testfor @p[r=10] {Inventory:[{tag:{display:{Name:"Item Name"}}}]}  /testfor @p[r=10] {SelectedItemSlot:0,Inventory:[{Slot:0b,­id:"minecraft:diamond_sword"}]­}   but I can't get them together. The block should only look for an item in the active slot. Suppose I have a node in the shape of a circle. How can I make its border thicker?   \node[circle, draw=blue!80, inner sep=0pt, minimum size=12pt] (1) at (0,0) {1}; Talk to him is what I did Talk to him is what I did.  (this sentence is from )  "Talk" is a verb here that is not in the imperative mood. I suppose, it's in the infinitive form. But then how can it stand alone, without "to"?  What will be if we add "to" to "talk"?  To talk to him is what I did.  If we can do so, then what will difference be between the initial sentence and the new one with "to"?  Maybe, there are some omitted words, after inserting which the sentence will immediately become understandable? I mean, maybe, there is an ellipsis?  Thanks!  To make it clearer:  Upd.1: if we type "bare infinitive" in google, we can't find any sites that could explain the absence from "to" before "talk".  Upd.2: Why can we replace "to talk" with only "talk" in "To talk to him is what I did."  Upd.3: I have my own logic but I don't know whether it's right or not:  1) I think that without an ellipsis "Talk to him is what I did." is to look like "I did talk to him is what I did do."  2) Also I know that we can't use "to" before "read" in "What we must do is read the manual." because in the left part we don't have "to" before "do".  By this logic, we can't use "to" before "talk" in "Talk to him is what I did." because in "what I did do" we don't have "to" before "do".  Am I right or not? Etymology of "cut someone some slack" Teenagers. All the literature tells you one thing and one thing only – that  whatever they are doing, give them a break, cut them some slack, it's normal.      From the novel, Apple Tree Yard   I'm curious about the origins of . I know slacks are American English for trousers or pants, and a slacker is a lazy person. But what is a slack and how does one "cut" it? DateTime "null" value I've been searching a lot but couldn't find a solution. How do you deal with a DateTime that should be able to contain an uninitialized value (equivalent to null)? I have a class which might have a DateTime property value set or not. I was thinking of initializing the property holder to DateTime.MinValue, which then could easily be checked. I guess this is a quite common question, how do you do that? Order of general- and special linear groups over finite fields. Let $\mathbb{F}_3$ be the field with three elements. Let $n\geq 1$. How many elements do the following groups have?   $\text{GL}_n(\mathbb{F}_3)$ $\text{SL}_n(\mathbb{F}_3)$   Here GL is the , the group of invertible n×n matrices, and SL is the , the group of n×n matrices with determinant 1. How to evaluate $\lim\limits_{n\to+\infty} \prod\limits_{k=1}^n (1+k/n^2)$? How do I calculate the determinant of the following $n\times n$ matrices  $$\begin {bmatrix} 0 &amp; 1 &amp; \ldots &amp; 1 \\ 1 &amp; 0 &amp; \ldots &amp; 1 \\ \vdots &amp; \vdots &amp; \ddots &amp; \vdots \\ 1 &amp; 1 &amp; ... &amp; 0 \end {bmatrix}$$  and the same matrix but one of columns replaced only with $1$s?  In the  above matrix all off-diagonal elements are $1$ and diagonal elements are $0$. Device : Moto X Play ( Rooted, Stock, Android 6.0.1, msm8916 Board, XT1562)  Why do I want to limit charging ?  ( Let's leave out whether my reasons are valid or not and accept that I want to, if you disagree with my reasons)  To improve the longevity of battery , I wish to limit charging when it reaches 90%, as explained here    Is it possible?  Yes, at least on my previous device Honor 6, as brought out here , with two different ways of doing it  I have tried  unsuccessfully to identify the file responsible in which changing values would limit charging  I am looking for the system file responsible for stopping charging, with it's true path (without symlinks)  (as I saw on on my previous device, locating the path of file was a big challenge after identifying it) making low-quality PDF files clearer Some research papers available on the web have low-quality outputs. For example, see . It seems that it was converted from a PS file and typeset in (La)TeX. However, it has all the font information. Is there any way to make the PDF file clearer? How to have a figure with caption in multicol environment? I am having the following problem with adding a figure inside the multicol environment:  \documentclass[10pt, twoside]{book} \usepackage{graphicx} \usepackage{subfig}  \begin{document}   \begin{multicols}{2}  a test file for picture inclusion along with the captions and labeling \begin{figure}  \centering  \includegraphics[width=5cma]{Cauchy_sequence_illustration-png}\\  \caption{Lets see}\label{pinki} \end{figure} \end{multicols}  \begin{figure}  \centering   \includegraphics[width=5cm]{Cauchy_sequence_illustration-png}\\  \caption{Lets see}\label{pinki} \end{figure}    \end{document}    After this while I am pressing Ctrl + Shift + X (usually I compile like this in DVI format and then clicking "dvi--->pdf" I convert it into PDF document.) the picture in multicol environment is not shown in YAP Viewer but the second one (which is outside of multicol environment) is shown along with the caption.  Kindly help me how to handle this problem. Please note that I am using the figure in .ps format. And I am not allowed to use any other format according to the instruction.