Documentation>vl_demo_svm

# Source code for ``vl_demo_svm.m

This file is located in the ``toolbox/demo folder in VLFeat package.

    % VL_DEMO_SVM  Demo: SVM: 2D linear learning
    function vl_demo_svm
    y=[];X=[];

    % Load training data X and their labels y
    load('vl_demo_svm_data.mat')

    Xp = X(:,y==1);
    Xn = X(:,y==-1);

    figure
    plot(Xn(1,:),Xn(2,:),'*r')
    hold on
    plot(Xp(1,:),Xp(2,:),'*b')
    axis equal ;
    vl_demo_print('svm_training') ;
    % Parameters
    lambda = 0.01 ; % Regularization parameter
    maxIter = 1000 ; % Maximum number of iterations

    energy = [] ;
    % Diagnostic function
    function diagnostics(svm)
      energy = [energy [svm.objective ; svm.dualObjective ; svm.dualityGap ] ] ;
    end

    % Training the SVM
    energy = [] ;
    [w b info] = vl_svmtrain(X, y, lambda,...
                               'MaxNumIterations',maxIter,...
                               'DiagnosticFunction',@diagnostics,...
                               'DiagnosticFrequency',1)

    % Visualisation
    eq = [num2str(w(1)) '*x+' num2str(w(2)) '*y+' num2str(b)];

    line = ezplot(eq, [-0.9 0.9 -0.9 0.9]);
    set(line, 'Color', [0 0.8 0],'linewidth', 2);

    vl_demo_print('svm_training_result') ;

    figure
    hold on
    plot(energy(1,:),'--b') ;
    plot(energy(2,:),'-.g') ;
    plot(energy(3,:),'r') ;
    legend('Primal objective','Dual objective','Duality gap')
    xlabel('Diagnostics iteration')
    ylabel('Energy')
    vl_demo_print('svm_energy') ;

    end