linregr.m

The following Matlab code converts a Matrix into it a diagonal and off-diagonal component and perfor

function [a,r2]=linregr(x,y)
n=length(x);
if length(y)~=n, error ('x and y must be same length ');
end

x=x(:); y=y(:);
sx= sum (x); sy= sum (y);
sx2= sum(x.*x);
sxy=sum(x.*y);
sy2= sum (y.*y);
a(1)= (n*sxy-sx*sy)/(n*sx2-sx^2);
a(2)=  sy/n-a(1)*sx/n;
r2=((n*sxy-sx*sy)/sqrt(n*sx2-sx^2)/sqrt(n*sy2-sy^2))^2
xp=linspace(min(x), max(x),2);
yp=a(1)*xp+a(2);
plot (x,y,'o',xp,yp)
grid on