How do I calculate the R^2?

n=100;

alpha=1;

beta=1.5;

e = randn(n,1);

x=rand(n,1);

y=alpha + x*beta + e;

x=[ones(n,1), x];

bhat = inv(x'*x)*x'*y;

disp 'The OLS estimate of beta is';

disp(bhat);

resids = y - x*bhat;

s2 = resids'*resids/(n-2);

disp 'The OLS estimator of the error variance is';

disp(s2);

Answer 1

[Jeff Miller]

Either of these:

Rsqr = corr(x(:,2),y)^2;
RsqrAlso = 1-(std(resids)/std(y))^2;