The point biserial correlation is used to measure the relationship between a binary variable, x, and a continuous variable, y. Like other correlation coefficients, this one varies between -1 and +1 with 0 implying no correlation. Correlations of -1 or +1 imply a determinative relationship.
x : array of bools
(point-biserial r, :
Missing values are considered pair-wise: if a value is missing in x, the corresponding value in y is masked.