Dataset examples

Dataset examples

Below some examples are given of dataset manipulations. Use is made of the PRTools command genlab(N) that generates a set of numeric labels, N(i) for class i. The command scatterd is similar but not identical to the Matlab command scatter and has thereby a similar, slightly different name.

    % delete all figure
    delfigs

    % reset random seed for repeatability
    % randreset(1)

    % Generate in 2 dimensions 3 normally distributed classes of 20 objects each
    a = dataset(randn(60,2),genlab([20 20 20]))
%        60 by 2 dataset with 3 classes: [20  20  20]

    % Give the features a name
    a = setfeatlab(a,char('size','intensity'))
%        60 by 2 dataset with 3 classes: [20  20  20]

    % Make the distributions of the classes different and plot them
    a(1:20,:) = a(1:20,:)*0.5;
    a(21:40,1) = a(21:40,1)+4;
    a(41:60,2) = a(41:60,2)+4;
    figure; scatterd(a)

    % create a subset of the second class
    b = a(21:40,:)
%        20 by 2 dataset with 3 classes: [0  20   0]

    % add 4 to the second feature of this class
    b(:,2) = b(:,2) + 4*ones(20,1)
%        20 by 2 dataset with 3 classes: [0  20   0]

    % concatenate this set to the original dataset
    c = [a;b]
%        80 by 2 dataset with 3 classes: [20  40  20]
    figure; scatterd(c);
    showfigs

For better annotation of the plot we may add some information on the dataset, the classes and features in some recognizable way, e.g.

    c = setname(c,'Fruit dataset');
    c = setlablist(c,char('apple','banana','cherry'));
    c = setfeatlab(c,char('size','weight'));
    figure; scatterd(c)

Dataset examples