PLA

pla.m

clear
close all
% Generate data
sample_size = 200;
A=repmat([2,2], sample_size,1)+randn(sample_size, 2);
B=repmat([-2,-2],sample_size,1)+randn(sample_size, 2);
X=[A; B];
Y=[ones(sample_size,1); -ones(sample_size,1)];
figure, plot(A(:,1),A(:,2),'ro'), hold on, plot(B(:,1),B(:,2),'xb');
pause;
% cycilc PLA
w=zeros(1,3);
Xext = [X ones(size(X,1), 1)];
num_mistake=1;
iter = 1;
while num_mistake > 0
    disp(['iteration= ' num2str(iter)]);
    % check for mistake
    err = sign(w*Xext') - Y';
    err_index=find(err);
    for t=1:length(err_index)
        w = w + Y(err_index(t))*Xext(err_index(t), :);
    end;
    
    num_mistake = length(err_index);
    iter = iter +1;
end;
% plot results: 2d line
range = axis;
ezplot([num2str(w(1)) '*x+' num2str(w(2)) '*y+' num2str(w(3))], range)