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 : bool, 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.
Examples
>>> x = np.ma.array(np.arange(8), mask=[0]*4 + [1]*4)
>>> np.ma.extras.median(x)
1.5
>>> x = np.ma.array(np.arange(10).reshape(2, 5), mask=[0]*6 + [1]*4)
>>> np.ma.extras.median(x)
2.5
>>> np.ma.extras.median(x, axis=1, overwrite_input=True)
masked_array(data = [ 2. 5.],
mask = False,
fill_value = 1e+20)