% [points]=datagen(sigma,inliers)
% 
% This function generates 100 2D POINTS of which 
% INLIERS are normally distributed 
% with standard deviation SIGMA 
% around a randomly generated line
% the remainder of the points are uniformly distributed in [-1,1]x[-1,1]

function [points]=datagen(sigma,inliers);

% generate random line
a=randn(2,1); a=a/norm(a);
b=rand(1)-0.5; % offset 
line=[a; b]; % line 
c=[a(2); -a(1)];
d=-a*b; % point closest to origin

% generate points on line
points=d*ones(1,inliers)+c*(2*rand(1,inliers)-1)+sigma*a*randn(1,inliers);
points=[points rand(2,100-inliers)*2-1];

figure(1);
clf;
plot(points(1,1:inliers),points(2,1:inliers),'x');
hold on
if (inliers<100)
    plot(points(1,inliers+1:100),points(2,inliers+1:100),'o');
end
hold off;
figure(2);
clf;
title('histogram of distance from line');
res=abs(line'*[points; ones(1,100)]);
bar(0:0.1:1,histc(res,0:0.1:1));