return array containing average of each of the specified columns

Question

I've been going crazy trying to find a way out.

Input a 2D array and several column numbers, return the average of every number in those specific columns in the form of array.

I know how to output the average of all columns, but I have no idea how to output only specific columns' averages.

a = array([[0, 0,1], [1, 1,2], [3, 3,3]])

get_average(a,[0,1])

array([1.333333333, 1.333333333333])

John1024 · Accepted Answer · 2014-11-13 05:17:36Z

1

numpy has an average function:

>>> import numpy as np
>>> a = np.array([[0, 0,1], [1, 1,2], [3, 3,3]])
>>> np.average(a[:,(0,1)], axis=0)
array([ 1.33,  1.33])

For np.average, axis specifies the array axis along with to average. axis=0, for example, averages over the rows.

np.average also offers weighted averages if you ever need them.

If you think you still want a get_average function, then:

def get_average(a, cols):
    return np.average(a[:,cols], axis=0)

answered Nov 13, 2014 at 4:45

John1024

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