What will be the value of AR and MA order?
Selecting ARIMA orders based on ACF-PACF vs. auto.arima
Using the residue theorem, calculate $\int_{0}^{2\pi}\frac{1}{1-2a\cos{\theta}+a^2}d\theta$ On finding polynomials that approximate a function and its derivative (extensions of Stone-Weierstrass?) I would like to have \alph{counter} for values larger than 26. The following MnWE gives me the error ! LaTeX Error: Counter too large.  \documentclass{article} \begin{document}  \begin{enumerate} \def\theenumi{\alph{enumi}} \setcounter{enumi}{24} \item twenty-five \item twenty-six \item twenty-seven \end{enumerate}  \end{document}   I would like it to behave like one of these:  ..., x, y, z, aa, bb, cc, ..., xx, yy, zz, aaa, bbb, ccc, ... (preferred) ..., x, y, z, aa, ab, ac, ..., ax, ay, az, ba,  bb,  bc,  ... (can be if nothing else works)   A solution without LaTeX3 extensions would be awesome as I cannot run LaTeX3 extensions. Why do we use residuals to test the assumptions on errors in regression? Suppose that we have a model $Y_i = \beta_0 + \beta_1X_{i1} + \beta_2X_{i2} + \dots + \beta_kX_{ik} + \epsilon_i$.  Regression has a number of assumptions, such as that the errors $\epsilon_i$ should be normally distributed with mean zero and constant variance. I have been taught to check these assumptions using a normal QQ plot to test for normality of the residuals $e_i = Y_i - \hat{Y}_i$ and a residuals vs. fitted plot to check that the residuals vary around zero with constant variance.  However, these tests are all on the residuals, not the errors.  From what I understand, the errors are defined as the deviation of each observation from their 'true' mean value. So, we can write $\epsilon_i = Y_i - \mathbb{E}[Y_i]$. These errors cannot be observed by us. *  My question is this: how good of a job do the residuals do in mimicking the errors?   If the assumptions appear to be satisfied on the residuals, does this mean they are satisfied on the errors too? Are there other (better) ways to test the assumptions, like fitting the model to a testing dataset and getting the residuals from there?    * Furthermore, does this not require that the model is specified correctly? That is, that the response really does have a relationship with the predictors $X_1, X_2,$ etc. in the way specified by the model.  If we are missing some predictors (say, $X_{k+1}\ \text{to}\ X_p$), then the expectation $\mathbb{E}[Y_i] = \beta_0 + \beta_1X_{i1} + \beta_2X_{i2} + \dots + \beta_kX_{ik}$ would not even be the true mean, and further analysis on an incorrect model seems pointless.  How do we check whether the model is a correct one? Index not created in pdf output, even though idx file is present I have a document that has \usepackage{makeidx} and \makeindex in the preamble and \printindex inside the document body. An .idx file is created when I compile, no errors are signalled, still there is no index listing in the PDF document that is produced. There used to be one until all my files were deleted except the .tex file, after that I could not get the index to appear in my output. How can one troubleshoot this thing? I have changed all the "%bm" with "%tm" wherever I could find it in the build profiles (Tools -> Options -> Clean), as Thorsten Donig suggested on this website (in an answer to another posting regarding problems with the index creation). It did not solve my problem. I am using the TeXnicCenter editor on Windows XP, with the MiKTeX 2.9 distribution. Comment authors are not getting migrated Can I use my single entry Schengen visa to go to a different Schengen country than originally planned? My friends and I planned to visit Germany, so I got a single entry tourist Schengen visa to Germany. However, my travel plans have changed since then, because my friends are going to Italy instead. I don't have time to apply for a visa to Italy, but I have been told that I can use my Schengen visa to enter Italy. Is that true? Check if antiderivative is elementary I was experimenting with various integration techniques, and I stumbled upon the integral:  $$ \int{\frac{\tan{x}}{x} dx} $$  I tried using a number of methods, but I could not solve it. Checking on WolframAlpha, I found that the integral does not have an elementary antiderivative. However, I am not satisfied with simply assuming it's non-elementary if I have difficulty in solving it.   My question: Is there a test to determine if an antiderivative is elementary or not? Can Ubuntu use all my 4GB of RAM? Show that for any $k$-cycle $(a_1 a_2...a_k) \in S_n$, and for any permutation $\pi \in S_n$, $\pi(a_1...a_k)\pi^{-1}=(\pi(a_1)..\pi(a_k))$ By accident, I messed up a configuration file. How do I recover the default version without reinstalling or affecting other things? Question list on profile page not vertically aligned Evaluate $\lim_{x \to 0} (x\lfloor\frac{1}{x}\rfloor)$ The Creative Commons FAQ      Third, if the licensor does not like how the material has been modified or used, CC licenses require that the licensee remove the attribution information upon request [...]  in 4.0, this also applies to the unmodified work.   How do I remove / dissociate my name from a post, in accordance with this clause?  Also, what are the effects of having my post dissociated from my account?  Finally, how will dissociation requests be handled for posts licensed under earlier versions of the license, which do not require dissociation upon request in all cases? When should I publish in interdisciplinary versus subject-specific scientific journals? What is the black thing on the circuit What is the black thing on the below circuit?   Is it used to hide the IC (or other components) that is used on the circuit?   What material is it? Why would parametric statistics ever be preferred over nonparametric? Can someone explain to me why would anyone choose a parametric over a nonparametric statistical method for hypothesis testing or regression analysis?   In my mind, it's like going for rafting and choosing a non-water resistant watch, because you may not get it wet. Why not use the tool that works on every occasion? What tool do I need to install to make my terminal show the autocompletion of the command that I'm writing? Suppose a package provides whatever.service file so certain events (including whatever.socket) cause a daemon to start with a certain configuration.  I want to disable this completely. In particular, I want the old socket and any other unit files that might refer to this service by name to be unable to start the daemon.  Instead, I want to create my own unit files for this daemon with a different .socket unit and different environment variables. I also want my override to automatically take account of possible upstream updates to the original unit file (which my current solution of copying whatever.service as whatever-modified.service and editing it unfortunately does not provide).  If I create the following symlinks and files: /etc/systemd/system/whatever.service → /dev/null /etc/systemd/system/whatever-modified.service → /usr/lib/systemd/system/whatever.service /etc/systemd/system/whatever-modified.service.d/fix.conf  systemd considers the new service to be masked as well and refuses to start it. How to avoid this? how to use dom php parser