Compute the median along the specified axis.
Returns the median of the array elements.
Parameters:  a : array_like
axis : int, optional
out : ndarray, optional
overwrite_input : {False, True}, optional


Returns:  median : ndarray.

See also
Notes
Given a vector V with N non masked values, the median of V is the middle value of a sorted copy of V (Vs)  i.e. Vs[(N1)/2], when N is odd, or {Vs[N/2  1] + Vs[N/2]}/2. when N is even.