% Demonstration of a very simple single layer perceptron learning for 2D
% data
% Coded by Md. Iftekhar Tanveer (go2chayan@gmail.com)
% http://www.itanveer.com
% Modified by Silvio Simani 26/10/2021
%

clear all, close all, clc

example = 1; % Normal dataset
%example = 2; % Normal dataset with some other y
%example = 3; % Normal dataset where some -1's are gone
%example = 4; % Normal dataset with added mass

eta = 0.7; % Learning rate
n_iter = 0;

% Normal Dataset
if(example == 1),
 X = [0,0;0,1;0,2;0,3;0,4;1,0;1,1;1,2;1,3;1,4;2,0;2,1;2,2;2,3;2,4;3,0;3,1;3,2;3,3;3,4;
      4,0;4,1;4,2;4,3;4,4];
 d = [-1;-1;-1;-1;-1;+1;-1;-1;-1;-1;+1;+1;-1;-1;-1;+1;+1;+1;-1;-1;+1;+1;+1;+1;-1];
end;
 
% Some other y
if(example == 2),
 X = [0,0;0,1;0,2;0,3;0,4;1,0;1,1;1,2;1,3;1,4;2,0;2,1;2,2;2,3;2,4;3,0;3,1;3,2;3,3;3,4;
      4,0;4,1;4,2;4,3;4,4];
 d = [+1;+1;-1;-1;-1;+1;+1;-1;-1;-1;+1;+1;-1;-1;-1;+1;+1;-1;-1;-1;+1;+1;-1;-1;-1;];
end;

% Some -1's are gone
if(example == 3),
 X = [0,0;0,1;0,2;1,0;1,1;1,2;1,3;2,0;2,1;2,2;2,3;2,4;3,0;3,1;3,2;3,3;3,4;
      4,0;4,1;4,2;4,3;4,4];
 d = [-1;-1;-1;+1;-1;-1;-1;+1;+1;-1;-1;-1;+1;+1;+1;-1;-1;+1;+1;+1;+1;-1];
end;

% With added mass
if(example == 4),
X = [0,0;0,1;0,2;0,3;0,4;1,0;1,1;1,2;1,3;1,4;2,0;2,1;2,2;2,3;2,4;3,0;3,1;3,2;3,3;3,4;
    4,0;4,1;4,2;4,3;4,4;0,-6;1,-6;2,-6;3,-6;4,-6;5,-6;6,-6];
d = [-1;-1;-1;-1;-1;+1;-1;-1;-1;-1;+1;+1;-1;-1;-1;+1;+1;+1;-1;-1;+1;+1;+1;+1;-1;
    +1;+1;+1;+1;+1;+1;+1];
end;

% Adding column of 1's in X for y-intercept of the line
X = [X,ones(length(d),1)];

% Least Square
%w = X\d;

w = [0,0,0];
clf
while(sum(sign(w*X')~=d')>0)
    for i = 1:length(d)
        scatter(X(:,1),X(:,2),[],d,'filled')
        hold on
        % Perceptron
        if(sign(w*X(i,:)')~=d(i)),
            %w = w + X(i,:)*d(i);
            w = w - eta*(sign(w*X(i,:)') - d(i))*X(i,:); % Learning rule
            n_iter = n_iter + 1;
        end
        
        strEq = sprintf('%f*x + %f*y + %f = 0',w(1),w(2),w(3));
        xx = -2:0.01:6;
        yy = -(w(1)/w(2))*xx - (w(3)/w(2));
        scatter(xx,yy,'.');
        hold off
        title(strEq);
        drawnow
        pause(0.3)
    end
end

n_iter