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Create an array which is the average of every consecutive subarray of given size using NumPy

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  • Last Updated : 02 Sep, 2020

In this article, we will see the program for creating an array of elements in which every element is the average of every consecutive subarrays of size k of a given numpy array of size n such that k is a factor of n i.e. (n%k==0). This task can be done by using numpy.mean() and numpy.reshape() functions together.

Syntax: numpy.mean(arr, axis = None)

Return: Arithmetic mean of the array (a scalar value if axis is none) or array with mean values along specified axis. 

Syntax: numpy_array.reshape(shape)

Return: It returns numpy.ndarray

Example :

Arr = [1,2,3,4,5,6
       7,8,9,10,11
       12,13,14,15,16] 
and K = 2 then 
Output is [ 1.5, 3.5, 5.5, 7.5, 
            9.5, 11.5, 13.5, 15.5].
            
Here, subarray of size k and there average are calculated as :

[1 2]    avg = ( 1 + 2 ) / 2 = 1.5  
[3 4]    avg = ( 3 + 4 ) / 2 = 3.5
[5 6]    avg = ( 5 + 6 ) / 2 = 5.5
[7 8]    avg = ( 7 + 8 ) / 2 = 7.5
[9 10]   avg = ( 9 + 10 ) / 2 = 9.5 
[11 12]  avg = ( 11 + 12 ) / 2 = 11.5 
[13 14]  avg = ( 13 + 14 ) / 2 = 13.5 
[15 16]  avg = ( 15 + 16 ) / 2 = 15.5

Below is the implementation:

Python3




# importing library
import numpy
  
# create numpy array
arr = numpy.array([1, 2, 3, 4, 5,
                   6, 7, 8, 9, 10,
                   11, 12, 13, 14,
                   15, 16])
  
# view array
print("Given Array:\n", arr)
  
# declare k
k = 2
  
# find the mean 
output = numpy.mean(arr.reshape(-1, k),
                    axis=1)
  
# view output
print("Output Array:\n", output)

Output:

Given Array:
[ 1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16]
Output Array:
[ 1.5  3.5  5.5  7.5  9.5 11.5 13.5 15.5]
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