How do I calculate r-squared using Python and Numpy?

Question

I\'m using Python and Numpy to calculate a best fit polynomial of arbitrary degree. I pass a list of x values, y values, and the degree of the polynomial I want to fit (lin

Answer 1

Here's a very simple python function to compute R^2 from the actual and predicted values assuming y and y_hat are pandas series:

def r_squared(y, y_hat):
    y_bar = y.mean()
    ss_tot = ((y-y_bar)**2).sum()
    ss_res = ((y-y_hat)**2).sum()
    return 1 - (ss_res/ss_tot)