Calculates the nth moment about the mean for a sample.
Generally used to calculate coefficients of skewness and
kurtosis.
Parameters :
a : array_like
data
moment : int
order of central moment that is returned
axis : int or None
Axis along which the central moment is computed. If None, then the data
array is raveled. The default axis is zero.
Returns :
n-th central moment : ndarray or float
The appropriate moment along the given axis or over all values if axis
is None. The denominator for the moment calculation is the number of
observations, no degrees of freedom correction is done.