PRTools Introductory Example

A very short intro into some of the PRTools possibilities and notation.

Make sure PRTools is in the path.

if exist('ldc','file') ~= 2
  error('PRTools is not in the path, please add it.')
end
disp([newline '--- Everything is fine ---'])

Get rid of old figures

delfigs

Take an arbitrary 2D dataset of two classes and plot it

A = gendatb; % The banana set
scatterd(A); % A scatterplot

The dataset A is a PRTools ‘object’. Typing A, without ‘;‘ gives some info:

A

It can be converted to a structure by

struct(A)

Its contents can be listed by

+A

The 2 feature values of the first 5 objects can be inspected by

+A(1:5,:)

Mark them in the scatterplot

hold on; scatterd(A(1:5,:),'o');

Compute a simple classifier: Fisher’s Linear Discriminant

W1 = A*fisherc;

Note that in PRTools A*PROC([],PARS) is an alternative for PROC(A,PARS)

The error on the training set

A*W1*testc

Plot it in the scatterplot

plotc(W1)

Compute a 3rd degree polynomial classifier based on fisherc and plot it

W2 = A*polyc([],fisherc,3);
plotc(W2,'r')

The error on the training set

A*W2*testc

Split for separate training and testing

[AT,AS] = gendat(A,0.5)              % 50-50 split in trainset and testset
W = AT*{fisherc,polyc([],fisherc,3)} % Train classifiers by AT
testc(AS,W)                          % Test  classifiers by AS