Equivalence class of polynomials in abstract algebra
Calculations in quotient rings
CSS customized scroll bar in div I have noticed that such terms as model hyperparameter and model parameter have been used interchangeably on the web without prior clarification. I think this is incorrect and needs explanation. Consider a machine learning model, an SVM/NN/NB based classificator or image recognizer, just anything that first springs to mind.   What are the hyperparameters and parameters of the model? Give your examples please. Array List count to users Best method for short time-series I have a question related to modeling short time-series. It is not a question , but how. What method would you recommend for modeling (very) short time-series (say of length $T \leq 20$)? By "best" I mean here the most robust one, that is the least prone to errors due the fact of limited numbers of observations. With short series single observations could influence the forecast, so the method should provide a cautious estimate of errors and possible variability connected to the forecast. I am generally interested in univariate time-series but it would be also interesting to know about other methods. Matrix doesn't shrink when put in fraction. I've been studying the postulates of QM and seeing how to derive important ideas from them. One thing that I haven't been able to derive from them, however, is the identity of the momentum operator.  For simplicity, I'm only thinking about no relativistic effects, no spin, no time-dependent potentials, and one spatial dimension. Also I'm assuming the position operator is simply multiplication by $x$, as in, I'm in position space. So the Hamiltonian operator is  $ H = -\frac{\hbar^2}{2m}\nabla^2+V$.  I know that the momentum operator is $p = -i\hbar \frac{\partial}{\partial x}$.  But how do I get there from the postulates? I know that it makes sense, as it results in the Ehrenfest Theorem, the De Broglie wavelength hypothesis, the Heisenberg Uncertainty Principle (for $x$ and $p$), the momentum operator being the generator of the translation operator, and possibly many other desirable theorems, and correlations with classical momentum.  But none of these are postulates (at least, not in the various formalisms I encountered), so you can't derive $p = -i\hbar \frac{\partial}{\partial x}$ from them. Rather, they are consequences of it. You need to know the operator beforehand to see that they are correct. Yes, this is just semantics, but that is the core issue for me:  Regardless of how much sense it makes, is the identity $p = -i\hbar \frac{\partial}{\partial x}$ (under the assumptions I made) a Postulate, meaning that you can't derive it from other postulates, or can it in fact be obtained from them? And in the latter case, could you show me how?  Note: I know that there are many different and equivalent sets of postulates for QM. But in none that I saw did they name it as a postulate nor properly derived it. Compile error: package javax.servlet does not exist How and when does the tracking of shared links work? I can't seem to get this hat on straight! I carefully positioned my hat to fit my head just right:     But it seems to be shifted to the left a few pixels elsewhere (same in Firefox and Chrome):   Stack Overfow   Skeptics   The top bar is also affected on some sites:   Stack Overfow   Meta SE   InfoSec   However, it is in the correct position in the top bar on some sites somehow:   Skeptics   Bricks   It's not a huge deal of course, it just bothers perfectionists like me. How to say that you have plans to go to the movies tonight (but you are not sure yet, maybe you will have a pizza)? I mean there are options:     I am going to the cinema tonight.   Way too much certainty in this. For me it means that you have already bought tickets, the least.     I am going to go to the cinema tonight.   Sounds a bit awkward.     I will go to the cinema tonight.   Sounds too formal to me. Why is my voice command missing from the ok glass menu in XE16? Alignment issue in 'Your Sites' section in the Android app Derive equation for a cantilever in SHM Why does the following code does'nt work when i am using PDFLaTeX or just LaTeX ? I tried it in different editors as well.  This is the code   $\{f^'_n\}$   Surprisingly it works on Math.SE site How to import a module given the full path? Is there way to move one vertex and make another move with it proportionally? I'll try to explain in this gif. I am doing this manually in 2 steps - rotate, scale. And I select all vertexes. Is there instrument rotate them in one step or can I move one and make other move too? I want to set up a diary that compiles in two different orders: One is work by day, the other is work by project according to tags I give to the particular chunks of work I did each day.   For example, I write my diary as usual in work by day form:  2/2/15  -- bought a new screwdriver (tag: car maintainence)   -- scetched my plan for world domination (tag: world domination)  3/4/15  -- started studying physics (tag: world domination)  -- finished tax declaraction (tag: burocracy)   Compiling by project would yield tags as sections:  car maintainence    -- 2/2/15: bought a new screwdriver  world domination  -- 2/2/15: scetched my plan for world domination  -- 3/4/15: started studying physics  burocracy  -- 3/4/15: finished tax declaraction   I know this is pretty close to the literal programming paradigm the whole LaTex documentation follows: A code chunks in a document can be compiled to two different orders: For human understanding and for use by the machine. However, I want two human readable versions --say pdf-files-- as output. Is there some package that helps? Gduated symbology not taking attribute into account using QGIS I m working on a project on QGIS. I have a point shapefile vector that represents my store. In the attribute table, i have bunch of data such as size, unit per transaction and most importantly store turnover. When I want to graduate the symbology, the turnover isn't present in the list I can choose from. Does someone know why, and how to fix it? Is the set of all functions $f:Z_+\rightarrow Z_+$ that are eventually constant countable. I have a Java String that contains XML, with no line feeds or indentations. I would like to turn it into a String with nicely formatted XML. How do I do this?  String unformattedXml = "&lt;tag&gt;&lt;nested&gt;hello&lt;/nested&gt;&lt;/tag&gt;"; String formattedXml = new [UnknownClass]().format(unformattedXml);   Note: My input is a String. My output is a String.   (Basic) mock result:    &lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;root&gt;   &lt;tag&gt;     &lt;nested&gt;hello&lt;/nested&gt;   &lt;/tag&gt; &lt;/root&gt;