I have a dataset with two features and one outcome.  I was asked to separate the data into three parts such that 70% of the data is a training set, 20% is for validation and 10% for testing. The model will be linear regression.  Why would I need both a validation set and test set here?  I am not selecting a type of model or tuning hyperparameters.    There are no options to select a model as it is a linear regression in the form of $y = b_1a_1 + b_2a_2 + b_3$, where we will get $b_1$, $b_2$, and $b_3$ from the training set. I will test the model with the test set and report the error. So what is the need for a validation set?
I found this confusing when I use the neural network toolbox in Matlab. It divided the raw data set into three parts:   training set validation set test set   I notice in many training or learning algorithm, the data is often divided into 2 parts, the training set and the test set.  My questions are:   what is the difference between validation set and test set?  Is the validation set really specific to neural network? Or it is optional. To go further, is there a difference between validation and testing in context of machine learning?
Can multiple different HTML elements have the same ID if they're different elements? Let $S = \{ax + by: x,y \in \mathbb{Z}\}$  and let $e &gt; 0$ be the smallest element in $S$. Prove that $e \mid a$, and hence prove that $e = \gcd(a,b)$  I'm afraid I can't provide much of my initial working here because I'm at a loss of how to start.  I suppose that to show $e\mid a$ I would have to show that $eg = a$ for some $g \in \mathbb{Z}$. But I have no idea how I would do this. mysql database no space available Building the connection between cosine similarity and correlation in R error tex capacity exceeded log files added Can Xdebug be triggered by Drush commands? I'm running into an issue with my Features modules and installation profile when installing the site with drush si. There are a number of probably related issues in the Features issue queue, but none with good solutions. The interesting part (mentioned in some of the issues) is that it works fine when installing the site through the browser, but fails when installing with drush si.  I have an idea of what's wrong, but need to confirm it. The only way I can think of confirming it is to step through the code with a debugger (Xdebug is what I have set up). So, is it possible to trigger Xdebug from a command run with Drush? Specifically, can I get Xdebug to kick in when I run drush si? Partial instead of full markers are shown in PGFplots When using  \documentclass{article} \usepackage{pgfplots} \begin{document} \begin{tikzpicture}         \begin{axis}                     \addplot             [                 red,                 solid,                 mark=x,                 domain=-3e-3:3e-3,                 samples=50             ]              {exp(-x^2/(2e-3^2))/(1e-3*sqrt(2*pi))};         \end{axis}     \end{tikzpicture}    \end{document}   the markers look fine, see    , but when I replace solid with, for instance, loosely dashed, so  \documentclass{article} \usepackage{pgfplots} \begin{document} \begin{tikzpicture}         \begin{axis}                     \addplot             [                 red,                 loosely dashed,                 mark=x,                 domain=-3e-3:3e-3,                 samples=50             ]              {exp(-x^2/(2e-3^2))/(1e-3*sqrt(2*pi))};         \end{axis}     \end{tikzpicture}    \end{document}   the markers only show partially instead of fully, see    . How can I use loosely dashed with full markers showing? New Google SEO benefit with SSL - with only a few sections in SSL, or always on? Is there a definitive list of which episodes / scenes that they used for the classic doctors in The Day of The Doctor? Here's my preamble:  \documentclass[11pt]{amsart} \usepackage{geometry}                % See geometry.pdf to learn the layout options. There are lots. \geometry{letterpaper}                   % ... or a4paper or a5paper or ...  %\geometry{landscape}                % Activate for for rotated page geometry %\usepackage[parfill]{parskip}    % Activate to begin paragraphs with an empty line rather than an indent \usepackage{graphicx} \usepackage{amssymb} \usepackage{epstopdf} \usepackage{float} \usepackage[normalem]{ulem}  \DeclareGraphicsRule{.tif}{png}{.png}{`convert #1 `dirname #1`/`basename #1 .tif`.png}  \title{\emph{Research Proposal:}\\Perceptual Effects of Cross-Contextualized Soundscapes within the Built Environment}   Here's what happens:    Any ideas? Massless charged particles Are there any massless (zero invariant mass) particles carrying electric charge?  If not, why not? Do we expect to see any or are they a theoretical impossibility? How was the binomial coefficient of the binomial theorem derived?  $$\frac{n!}{k!(n-k)!}$$ How do you determine the winner of a hand? In Texas Hold'em poker, there are some cases where a particular card, often called kicker, acts as a tiebreaker between players to determine who wins the pot, or if the pot has to be shared.  For some combinations such as three or four of a kind, there is no doubt: the kicker is the 5th card of the chosen combination, and determines the winner.  Example     Alice has 7 and 10   Bob has 7 and K   On the board are 7, 7, 2, 3, 4   In that case, both have a three of a kind. But because Bob has a king and Alice only a 10, he wins.  Most of poker websites explaining the rules clearly mention the role of the kicker applying to three of a kind and double pairs. But much fewer say something about colors, straights and full houses, and I found many contradicting answers. I also asked the question to some used online poker players and they also gave me contradicting answers.  I have tried to search for official tournament rules, but most of them only explain what happens with bad behaviors, bad deals, incorrect or confusing betting, showing cards when you shouldn't, acting when it's not your turn, etc. without mentioning subtleties about combinations at all.  To simplify my question, I will take three examples; I think it's better to start with examples before getting to the general answer if one exists. So, what's happening in the following 3 examples? Could you give a more generalized answer?  Example 1 - Flushes     Alice has 2&clubs; and 3&clubs;   Bob has 4&clubs; and 5&clubs;   On the board are 6&clubs;, 8&clubs;, 10&clubs;, 2&hearts;, 5&diams;   Contradicting answer 1: it's a tie, because the highest card included in the flush is the 10, which everybody chooses to include in their 5 showdown cards. Contradicting answer 2: Bob wins, because he has the greatest private card that is part of the flush  Example 2 - Straight     Alice has 6 and K   Bob has 6 and J   On the board are 4, 5, 7, 8, 10   Contradicting answer 1: it's a tie, because the greatest card in the straight is the 8 for both Alice and Bob Contradicting answer 2: Alice wins, because she owns an extra king, compared to the jack of Bob  Example 3 - Full house     Alice has 3 and 7   Bob has 3 and 6   On the board are 3, 3, 2, 2, 5   Contradicting answer 1: it's a tie, because one is supposed to choose only five cards to make a combination, and a full house is already five cards. There couldn't be any kicker, and thus their showdowns are strictly equals. Contradicting answer 2: Alice wins because of her extra 7, compared to the 6 of Bob  Thank you very much for your answers.  Note: I'm unable to post next to you, so I edit my own post; strange not be able to answer to an answer.  Ok, So if I summarize what you are saying :   In the flush case, Bob wins because at some point, their hand differs. Technically, I can continue comparing the highest private card to decide who wins. I had it correct. In the straight case, if the highest card of the straight is public, then it's technically always a tie, no matter what the players had as second private card (asuming that only one of the two cards was part of the straight). In a full house if both players have the same triplet and the same pair, it's always a tie, no matter what the players had as second private card (assuming again that only one of the two was part of the full house).   Please confirm me that what I summarized is correct.  Thank you for your answer. 8 GB RAM installed, only 7.5 GB usable. Windows 7 64-bit I just upgraded my computer's RAM, adding another 4 GB to the computer.  Windows 7 acknowledges that 8 GB is installed, but says only 7.5 GB is accessible.  Any idea why? I thought since I had the 64-bit Professional version this wouldn't be an issue. distribution with point support Set Windows process (or user) memory limit Is there any way to set a system wide memory limit a process can use in Windows XP? I have a couple of unstable apps which do work ok for most of the time but can hit a bug which results in eating whole memory in a matter of seconds (or at least I suppose that's it). This results in a hard reset as Windows becomes totally unresponsive and I lose my work.  I would like to be able to do something like the /etc/limits on Linux - setting M90, for instance (to set 90% max memory for a single user to allocate). So the system gets the remaining 10% no matter what. How should a family with young children apply for UK visas? We are sponsoring a family to visit us in UK as friends from Madagascar for two weeks. They have a 6 year old and a 16 month old.   Do the kids need their own visas, and are they the standard visitor visa or a special child visa?   Also, when I try and apply on the website I can only apply for one person so how do I apply for all the individuals in the family?   I have looked on the Immigration website and can't find the answers I need. I accidentally deleted a file from my laptop. I'm using Fedora. Is it possible to recover the file? Better understanding of Drupal behaviors I read about Drupal behaviors today, and I tried writing the following code.  (function ($) {    Drupal.behaviors.mymodule = {     attach: function (context, settings) {       $('#mymodule_id', context).change(function () {         alert('Handler for .change() called.');       });     }   };  }(jQuery));    Is Drupal.behaviors.mymodule the namespace? What are the context and settings parameters passed to the Drupal behavior? Is this the equivalent of document.ready()?   Can I attach any number of functions?  Can I define JavaScript functions which will be called somewhere? Screen Resolution Problem with Ubuntu 14.04 and VirtualBox