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<html><head> <meta HTTP-EQUIV="Content-Type" CONTENT="text/html;charset=ISO-8859-1"> <title>mahalan.m</title><link rel="stylesheet" type="text/css" href="../../m-syntax.css"></head><body><code><span class=defun_kw>function</span> <span class=defun_out>dist </span>= <span class=defun_name>mahalan</span>(<span class=defun_in>X,Mean,Cov</span>)<br><span class=h1>% MAHALAN Computes Mahalanobis distance.</span><br><span class=help>%</span><br><span class=help>% <span class=help_field>Synopsis:</span></span><br><span class=help>% dist = mahalan(X,Mean,Cov)</span><br><span class=help>%</span><br><span class=help>% <span class=help_field>Description:</span></span><br><span class=help>% It computes Mahalanobis distance between column vectors </span><br><span class=help>% of matrix X and vector Mean with matrix Cov, i.e.,</span><br><span class=help>%</span><br><span class=help>% dist(i) = (X(:,i)-Mean)'*inv(C)*(X(:,i)-Mean)</span><br><span class=help>%</span><br><span class=help>% for all i=1:size(X,2).</span><br><span class=help>%</span><br><span class=help>% <span class=help_field>Input:</span></span><br><span class=help>% X [dim x num_data] Input data.</span><br><span class=help>% Mean [dim x 1] Vector.</span><br><span class=help>% Cov [dim x dim] Matrix.</span><br><span class=help>%</span><br><span class=help>% <span class=help_field>Output:</span></span><br><span class=help>% dist [1 x num_data] Mahalanobis distance.</span><br><span class=help>%</span><br><span class=help>% <span class=help_field>Example:</span></span><br><span class=help>% It plots isolines of Mahalanobis distance.</span><br><span class=help>%</span><br><span class=help>% [Ax,Ay] = meshgrid(linspace(-5,5,100), linspace(-5,5,100));</span><br><span class=help>% dist = mahalan([Ax(:)';Ay(:)'],[0;0],[1 0.5; 0.5 1]);</span><br><span class=help>% figure; contour( Ax, Ay, reshape(dist,100,100));</span><br><span class=help>%</span><br><hr><span class=help1>% <span class=help1_field>About:</span> Statistical Pattern Recognition Toolbox</span><br><span class=help1>% (C) 1999-2003, Written by Vojtech Franc and Vaclav Hlavac</span><br><span class=help1>% <a href="http://www.cvut.cz">Czech Technical University Prague</a></span><br><span class=help1>% <a href="http://www.feld.cvut.cz">Faculty of Electrical Engineering</a></span><br><span class=help1>% <a href="http://cmp.felk.cvut.cz">Center for Machine Perception</a></span><br><br><span class=help1>% <span class=help1_field>Modifications:</span></span><br><span class=help1>% 28-apr-2004, VF</span><br><br><hr>[dim, num_data] = size( X );<br><br>XC = X - repmat(Mean,1,num_data);<br>dist= sum((XC<span class=quotes>'*inv( Cov ).*XC'</span>)',1);<br><br><span class=jump>return</span>;<br></code>?? 快捷鍵說明
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