R2 returning negative values

[rajanikant-ghate]

R2 can have negative values if the chosen model is worst than a horizontal line (slope of 0). The interpretation of negative R2 is no different than what it would be for 0. However, in practice with some real data, practically all R2 will be between 0 and 1, unless an intercept is constraint in unrealistic manner, or when worked with very few sample points.