regularized correlation

regularized_correlation.py

def regularized_correlation(size, dot_product, rating_sum, \
            rating2sum, rating_norm_squared, rating2_norm_squared,
            virtual_cont, prior_correlation):
    '''
    The Regularized Correlation between two vectors A, B

    RegularizedCorrelation = w * ActualCorrelation + (1 - w) * PriorCorrelation
        where w = # actualPairs / (# actualPairs + # virtualPairs).
    '''
    unregularizedCorrelation = correlation(size, dot_product, rating_sum, \
            rating2sum, rating_norm_squared, rating2_norm_squared)

    w = size / float(size + virtual_cont)

    return w * unregularizedCorrelation + (1.0 - w) * prior_correlation