Average values in two Numpy arrays

Given two ndarrays

old_set = [[0, 1], [4, 5]]
new_set = [[2, 7], [0, 1]]

I'm looking to get the mean of the respective values between the two arrays so that the data ends up something like:

end_data = [[1, 4], [2, 3]]

basically it would apply something like

for i in len(old_set):
    end_data[i] = (old_set[i]+new_set[i])/2

But I'm unsure what syntax to use.. Thanks for the help in advance!

You can create a 3D array containing your 2D arrays to be averaged, then average along axis=0 using np.mean or np.average (the latter allows for weighted averages):

np.mean( np.array([ old_set, new_set ]), axis=0 )

This averaging scheme can be applied to any (n)-dimensional array, because the created (n+1)-dimensional array will always contain the original arrays to be averaged along its axis=0.

>>> import numpy as np
>>> old_set = [[0, 1], [4, 5]]
>>> new_set = [[2, 7], [0, 1]]
>>> (np.array(old_set) + np.array(new_set)) / 2.0
array([[1., 4.],
       [2., 3.]])

Using numpy.average

Also numpy.average can be used with the same syntax:

import numpy as np
a = np.array([np.arange(0,9).reshape(3,3),np.arange(9,18).reshape(3,3)])
averaged_array = np.average(a,axis=0)

The advantage of numpy.average compared to numpy.mean is the possibility to use also the weights parameter as an array of the same shape:

weighta = np.empty((3,3))    
weightb = np.empty((3,3))       
weights = np.array([weighta.fill(0.5),weightb.fill(0.8) ])
np.average(a,axis=0,weights=weights)

If you use masked arrays consider also using numpy.ma.average because numpy.average don't deal with them.