I know how to interpret residuals in a linear regression model. I am now working in a model that predicts a binary target combining numerical and categorical variables.  My residual plots is as follows:     If this were residual plots from a linear regression model I would be able to interpret them and notice that they are terrible. However I do not know if the same interpretation must be done when working with a logistic regression model.
Can anyone tell me how to interpret the 'residuals vs fitted', 'normal q-q', 'scale-location', and  'residuals vs leverage' plots?  I am fitting a binomial GLM, saving it and then plotting it.
What is the most elegant way to solve this:   open a file for reading, but only if it is not already opened for writing open a file for writing, but only if it is not already opened for reading or writing   The built-in functions work like this  &gt;&gt;&gt; path = r"c:\scr.txt" &gt;&gt;&gt; file1 = open(path, "w") &gt;&gt;&gt; print file1 &lt;open file 'c:\scr.txt', mode 'w' at 0x019F88D8&gt; &gt;&gt;&gt; file2 = open(path, "w") &gt;&gt;&gt; print file2 &lt;open file 'c:\scr.txt', mode 'w' at 0x02332188&gt; &gt;&gt;&gt; file1.write("111") &gt;&gt;&gt; file2.write("222") &gt;&gt;&gt; file1.close()   scr.txt now contains '111'.  &gt;&gt;&gt; file2.close()   scr.txt was overwritten and now contains '222' (on Windows, Python 2.4).  The solution should work inside the same process (like in the example above) as well as when another process has opened the file. It is preferred, if a crashing program will not keep the lock open. SQL Server CE in a multi user scenario - is this really, really stupid? Are two norms equivalent if they induce the same topology on a vector space? Helix on a cylinder Showing $\sum_{i = 1}^n\frac1{i(i+1)} = 1-\frac1{n+1}$ without induction? I oversaw a high-school mathematics test the other day, and one of the problems was the following     Show, using induction or other means, that $$\sum_{i = 1}^n\frac1{i(i+1)} = 1-\frac1{n+1}$$   The induction proof is very standard, where the induction step relies on the fact that $\frac{1}{n+1} + \frac{1}{n(n+1)} = \frac{1}{n}$, and I'm sure it's been answered on this site before. However, I got intrigued by the "or other means" part of the question.  I don't know whether the teacher who wrote the test even considered any alternative solutions (he may just have written it so that if anyone has a crazy idea that works out, then they should get a full score for it), but I tried to find one. For instance, we may do the following telescope-ish argument: $$ \frac{1}{1(1+1)} + \frac{1}{2(2+1)} + \cdots + \frac{1}{(n-1)n} + \frac{1}{n(n+1)} + \frac{1}{n+1}\\ = \frac{1}{1(1+1)} + \frac{1}{2(2+1)} + \cdots + \frac{1}{(n-1)n} + \frac1n\\ \vdots\\ = \frac{1}{1(1+1)} + \frac12\\ = 1 $$ However, I feel that this is just an induction proof in disguise (hidden in the vertical dots). If one uses the mechanics of the induction proof to check whether the formula is true for a specific $n$, then one certainly does the exact same calculations as I have done here.  Is there a proof of this fact that clearly does not use induction (or at least hides it better)? The more elementary the better, and the ultimate goal would be to do it within the syllabus of the students taking the test (or at least not far from it). For reference, they should be familiar with the summation formula of arithmetic and geometric series and their derivations (so techniques resembling those would be well within specifications).  If there is a solution using calculus, then the students should be able to integrate elementary trigonometric functions, as well as exponential functions, logarithms and rational functions. They are familiar with integration by parts, substitution and partial fractions.  I welcome more advanced solutions as well, of course. Does iOS support a built-in firewall like macOS does? I don't see anything about it in Settings. In the answer , the parser breaks my URL link.  The URL was with __word__:      http://www.open-mpi.de/projects/hwloc/doc/v1.2/group__hwlocality__membinding.php#gade5e2c28ea8475a479bf2b1df36c6ccd   After parsing, it becomes (&lt;a href is broken; no clickable link):  hwlocality_membinding.php#gade5e2c28ea8475a479bf2b1df36c6ccd"&gt;http://www.open-mpi.de/projects/hwloc/doc/v1.2/group_hwlocality_membinding.php#gade5e2c28ea8475a479bf2b1df36c6ccd   Short test:  http://example.com/_test_ -> test"&gt;http://example.com/test  Or if I put in a naked URL with _test_ just here: The  currently says  In the context of Stack Exchange sites, any copying and pasting of any amount of text or code that wasn't written by you is plagiarism if you try, explicitly or implicitly, to pass it off as your own work. (italics mine)  There is also a concept of . Should this also be addressed in the FAQs? In other words, is it OK to copy (large parts of) your own answer  without proper attribution? For a physics major, what are the best books/references on Greens functions for self-studying?  My mathematical background is on the level of Mathematical Methods in the physical sciences by Mary Boas. Why is $a^n - b^n$ divisible by $a-b$? I did some mathematical induction problems on divisibility   $9^n$ $-$ $2^n$ is divisible by 7. $4^n$ $-$ $1$ is divisible by 3. $9^n$ $-$ $4^n$ is divisible by 5.   Can these be generalized as $a^n$ $-$ $b^n$$ = (a-b)N$, where N is an integer? But why is $a^n$ $-$ $b^n$$ = (a-b)N$ ?  I also see that $6^n$ $- 5n + 4$ is divisible by $5$ which is $6-5+4$ and $7^n$$+3n + 8$ is divisible by $9$ which is $7+3+8=18=9\cdot2$.  Are they just a coincidence or is there a theory behind?  Is it about modular arithmetic? Light Presets .exr I would like to install light presets for Blender to automate my lightning in my scenes. I have some .exr files (from Greyscalegorilla) but I don't know how to do it on Blender to make it work. Can someone help me? Thank you How to pass data from Javascript to PHP and vice versa? How to use downloaded fonts with pdfLaTeX on Ubuntu I want to use the  font in my pdfLatex document.  What steps should I do for using a downloaded font   Should I download the TTF or the OpenType version? Where should I store the font? Should any font processing be done? How can pdfLatex find this font?   I am using TexLive 2011 installed in a custom location (/somepath/texlive/2011) on Ubuntu Xpath expression with multiple predicates Story about human space explorers who run into alien telepath space crew I read a short story in an anthology around 1998 (the book could have been older than that) which went like this - A human space exploration scientific crew is exploring an alient planet (peaceful planet, as I recall) when they run into an alien spaceship (from a different planet which also happened to be there) - the aliens were telepaths.   The alien commander and first officer discuss the earthlings after a meeting and realize that the human crew are the descendants of a species (Banthu/Klanthu/Zantha, something like that) which had tried to violently take over the galaxy some 20/30/50,000 years ago and which had been beaten back by the combined might of the rest of the galaxy. They had supposedly been eliminated but they somehow managed to survive and are back in space only a few thousand years after they were completely beaten (which is something the aliens are amazed by).   The alien commander kills the human explorers via telepathy but realizes that there is no information available to locate their home planet and speculate that they will be meeting again soon given the past history of the humans.  I vaguely think there was also a fantasy short by L Sprague de Camp in the same anthology, but can't be 100% sure. Any thoughts/ideas? Thanks! In CodeGear Delphi 2007, how can I turn specific warnings and hints off? I am attempting to turn off H2077 - Value assigned to 'varname' never used. List files in a specific folder in a document library I there anyway to output the files of a specific folder in a document library?  Listing them will be like   foreach $file in $folder.files {     write-host $file.name }    But how do I tell it to look a specific folder? In CSOM please Tried the below answer but it did not work $I_m - AB$ is invertible if and only if $I_n - BA$ is invertible. The problem is from  Algebra by Artin, Chapter 1, Miscellaneous Problems, Exercise 8. I have been trying for a long time now to solve it but I am unsuccessful.      Let $A,B$ be $m \times n$ and $n \times m$ matrices. Prove that $I_m - AB$ is invertible if and only if $I_n - BA$ is invertible.    Please provide with only a hint. Multiple outputs for beamer handouts I'm currently generating some presentations with beamer for students of my course. Some like to print the material, so I created a handout. Some students prefer to have 2,3,4,6 etc. pages per sheet of A4 paper. How can I go about to automatize the following code, so that it outputs 4 different files in 1x2,1x3,2x2,2x3 format?  I'd like to avoid having to compile it again everytime for the different formats.  \documentclass[a4paper]{article} \usepackage{pdfpages}  \begin{document} \includepdf[pages=1-last,nup=1x2,landscape=false,frame=true,             noautoscale=false,scale=1,delta=0mm 5mm]{Pres7Chap13-Handout.pdf} \end{document} Logistic regression cost surface not convex I am building a simple logistic regression model on 2D data. Here is the input I use.    I built a logistic regression model using this data and it successfully is able to find the discriminating line between these two classes. Here is the separating line found by my program:    Also, just for debugging, I plotted number of iterations vs J(theta), which also looks fine:    Now, confusing part comes into play. I am investigating the cost surface of this model that the logistic regressions is doing the gradient descent on. I am considering three different loss functions. Sum-of-squared loss, hinge-loss, log-loss.  Hinge loss:    Log-loss:    Sum-of-squared loss:    As far as I know, both hinge loss, sum-of-squared loss and log-loss should produce a convex surface. When I look at my surfaces, however, sum-of-squared surface does not look convex to me. Why is that the case?  For convenience, here is the two critical functions from my code:  function retval = J(X, y, theta)     M = size(y, 1);     % sum of squared error     retval = (1/(2*M)) * sum((h(X, theta) - y).^2);  endfunction  function retval = h (X, theta)     % logistic     retval =  1 ./ (1+ exp(-1 * (X * theta))); endfunction