Gini returns the Gini coefficient. It is a measure of inequality in a frequency distribution. 0 indicates perfect equality, 1 maximum inequality.
Normal returns the y value at the given x of the standard unit normal distribution (mean = 0 and standard deviation = 1).
NormalArea calculates the area below the normal curve.
den = 2^n*n!*(2*n+1)
x - x(3,5,7...) / den
Pearson returns the Pearson correlation coeficient of two arrays
Not accurate and not faster than Go's own math.Sqrt