Statistical functions for tutorial purposes.
Work in progress on tutorial of using Statistics in programing .....
Example :
> x = np.array([1,2,3,4,5])
> np.var(x)
: 2.0
> stats.var(x)
: 2.5
> stats.var(x,sample=False)
: 2.0
> stats.cov(x,x,sample=False)
: 2.0