\section{Information\+Gain Class Reference}
\label{classmlpack_1_1tree_1_1InformationGain}\index{Information\+Gain@{Information\+Gain}}


The standard information gain criterion, used for calculating gain in decision trees.  


\subsection*{Static Public Member Functions}
\begin{DoxyCompactItemize}
\item 
{\footnotesize template$<$bool Use\+Weights$>$ }\\static double \textbf{ Evaluate} (const arma\+::\+Row$<$ size\+\_\+t $>$ \&labels, const size\+\_\+t num\+Classes, const arma\+::\+Row$<$ double $>$ \&weights)
\begin{DoxyCompactList}\small\item\em Given a set of labels, calculate the information gain of those labels. \end{DoxyCompactList}\item 
{\footnotesize template$<$bool Use\+Weights, typename Count\+Type $>$ }\\static double \textbf{ Evaluate\+Ptr} (const Count\+Type $\ast$counts, const size\+\_\+t count\+Length, const Count\+Type total\+Count)
\begin{DoxyCompactList}\small\item\em Evaluate the Gini impurity given a vector of class weight counts. \end{DoxyCompactList}\item 
static double \textbf{ Range} (const size\+\_\+t num\+Classes)
\begin{DoxyCompactList}\small\item\em Return the range of the information gain for the given number of classes. \end{DoxyCompactList}\end{DoxyCompactItemize}


\subsection{Detailed Description}
The standard information gain criterion, used for calculating gain in decision trees. 

Definition at line 25 of file information\+\_\+gain.\+hpp.



\subsection{Member Function Documentation}
\mbox{\label{classmlpack_1_1tree_1_1InformationGain_a82f0cda1eb3b481f5fec6142e07b8053}} 
\index{mlpack\+::tree\+::\+Information\+Gain@{mlpack\+::tree\+::\+Information\+Gain}!Evaluate@{Evaluate}}
\index{Evaluate@{Evaluate}!mlpack\+::tree\+::\+Information\+Gain@{mlpack\+::tree\+::\+Information\+Gain}}
\subsubsection{Evaluate()}
{\footnotesize\ttfamily static double Evaluate (\begin{DoxyParamCaption}\item[{const arma\+::\+Row$<$ size\+\_\+t $>$ \&}]{labels,  }\item[{const size\+\_\+t}]{num\+Classes,  }\item[{const arma\+::\+Row$<$ double $>$ \&}]{weights }\end{DoxyParamCaption})\hspace{0.3cm}{\ttfamily [inline]}, {\ttfamily [static]}}



Given a set of labels, calculate the information gain of those labels. 

Note that it is possible that due to floating-\/point representation issues, it is possible that the gain returned can be very slightly greater than 0! Thus, if you are checking for a perfect fit, be sure to use \textquotesingle{}gain $>$= 0.\+0\textquotesingle{} not \textquotesingle{}gain == 0.\+0\textquotesingle{}.


\begin{DoxyParams}{Parameters}
{\em labels} & Labels of the dataset. \\
\hline
{\em num\+Classes} & Number of classes in the dataset. \\
\hline
{\em weights} & Weights associated with labels. \\
\hline
\end{DoxyParams}


Definition at line 60 of file information\+\_\+gain.\+hpp.

\mbox{\label{classmlpack_1_1tree_1_1InformationGain_a67d1277fdaf085606937d4b523f615ba}} 
\index{mlpack\+::tree\+::\+Information\+Gain@{mlpack\+::tree\+::\+Information\+Gain}!Evaluate\+Ptr@{Evaluate\+Ptr}}
\index{Evaluate\+Ptr@{Evaluate\+Ptr}!mlpack\+::tree\+::\+Information\+Gain@{mlpack\+::tree\+::\+Information\+Gain}}
\subsubsection{Evaluate\+Ptr()}
{\footnotesize\ttfamily static double Evaluate\+Ptr (\begin{DoxyParamCaption}\item[{const Count\+Type $\ast$}]{counts,  }\item[{const size\+\_\+t}]{count\+Length,  }\item[{const Count\+Type}]{total\+Count }\end{DoxyParamCaption})\hspace{0.3cm}{\ttfamily [inline]}, {\ttfamily [static]}}



Evaluate the Gini impurity given a vector of class weight counts. 



Definition at line 32 of file information\+\_\+gain.\+hpp.

\mbox{\label{classmlpack_1_1tree_1_1InformationGain_a9d801bb1be5db5207213f846f224458f}} 
\index{mlpack\+::tree\+::\+Information\+Gain@{mlpack\+::tree\+::\+Information\+Gain}!Range@{Range}}
\index{Range@{Range}!mlpack\+::tree\+::\+Information\+Gain@{mlpack\+::tree\+::\+Information\+Gain}}
\subsubsection{Range()}
{\footnotesize\ttfamily static double Range (\begin{DoxyParamCaption}\item[{const size\+\_\+t}]{num\+Classes }\end{DoxyParamCaption})\hspace{0.3cm}{\ttfamily [inline]}, {\ttfamily [static]}}



Return the range of the information gain for the given number of classes. 

(That is, the difference between the maximum possible value and the minimum possible value.)


\begin{DoxyParams}{Parameters}
{\em num\+Classes} & Number of classes in the dataset. \\
\hline
\end{DoxyParams}


Definition at line 203 of file information\+\_\+gain.\+hpp.



The documentation for this class was generated from the following file\+:\begin{DoxyCompactItemize}
\item 
/var/www/mlpack.\+ratml.\+org/mlpack.\+org/\+\_\+src/mlpack-\/git/src/mlpack/methods/decision\+\_\+tree/\textbf{ information\+\_\+gain.\+hpp}\end{DoxyCompactItemize}