Documentation>vl_demo_gmm_2d_twist

# Source code for ``vl_demo_gmm_2d_twist.m

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

    %% data init
    numClusters = 30;
    dimension = 2;
    cc=hsv(numClusters);
    X = [];

    a = 0.9;
    t = linspace(0,4*pi,numClusters);
    x = a*(t.*cos(t));
    y = a*(t.*sin(t));
    mu = [x;y];

    Ns = linspace(1,numClusters,numClusters) * 20;

    for i=1:numClusters
        add = randn(dimension,Ns(i)) + repmat(mu(:,i),1,Ns(i));
        X = [X, add*50];
    end
    X = single(X);

    %% KMeans
    elapsedKMEANS = tic;
    [initMeans, assignments] = vl_kmeans(X, numClusters, ...
        'Verbose', ...
        'Algorithm','ann', ...
        'MaxNumIterations',5, ...
        'Distance','l2', ...
        'NumTrees',3, ...
        'MaxNumComparisons', 20);
    elapsedKMEANS = toc(elapsedKMEANS);
    fprintf('\n ---------- \n KMeans time - %f \n ---------- \n\n',elapsedKMEANS);

    initSigmas = zeros(dimension,numClusters);
    initWeights = zeros(1,numClusters);

    figure(1) ; clf ;
    subplot(3,1,1) ; hold on ;
    for i=1:numClusters
        Xk = X(:,assignments==i);

        initWeights(i) = size(Xk,2) / numClusters;

        plot(Xk(1,:),Xk(2,:),'.','color',cc(i,:));
        if size(Xk,1) == 0 || size(Xk,2) == 0
            initSigmas(:,i) = diag(cov(X'));
        else
            initSigmas(:,i) = diag(cov(Xk'));
        end
    end
    axis equal
    set(gca,'xtick',[],'ytick',[]);
    axis off
    title('GMM: KMeans intialization');

    initSigmas = single(initSigmas);
    initWeights = single(initWeights);

    %% GMM kmeans
    elapsedGMM = tic ;
    [means,sigmas,weights,ll,posteriors] = vl_gmm(X, numClusters, ...
        'Initialization','custom', ...
        'InitMeans',initMeans, ...
        'InitCovariances',initSigmas, ...
        'InitPriors',initWeights, ...
        'verbose', ...
        'MaxNumIterations', 20);
    elapsedGMM = toc(elapsedGMM);
    fprintf('\n ---------- \n GMM time - %f \n ---------- \n',elapsedGMM);

    subplot(3,1,2) ; hold on ;
    [~,idx] = max(posteriors,[],1);
    for i=1:numClusters
        plot(X(1,idx == i),X(2,idx == i),'.','color',cc(i,:));
        vl_plotframe([means(:,i)' sigmas(1,i) 0 sigmas(2,i)]);
    end
    title('GMM: Gaussian mixture - kmeans init');
    set(gca,'xtick',[],'ytick',[]);
    axis off
    axis equal

    %% GMM random
    elapsedGMM = tic;
    [means,sigmas,weights,ll,posteriors] = vl_gmm(X, numClusters, ...
        'Initialization','rand', ...
        'Verbose', ...
        'MaxNumIterations', 100);
    elapsedGMM = toc(elapsedGMM);
    fprintf('\n ---------- \n GMM time - %f \n ---------- \n',elapsedGMM);

    subplot(3,1,3) ; hold on ;
    [~,idx] = max(posteriors,[],1);
    for i=1:numClusters
        plot(X(1,idx == i),X(2,idx == i),'.','color',cc(i,:));
        vl_plotframe([means(:,i)' sigmas(1,i) 0 sigmas(2,i)]);
    end
    title('GMM: Gaussian mixture - random init');
    axis equal
    set(gca,'xtick',[],'ytick',[]);
    axis off
    vl_demo_print('gmm_2d_shell',1.2);