NumPy: Calculate cumulative product of the elements along a given axis

Last update on August 29 2025 12:44:50 (UTC/GMT +8 hours)

28. Cumulative Product and Row/Column Products

Write a NumPy program to calculate cumulative product of the elements along a given axis, sum over rows for each of the 3 columns and product over columns for each of the 2 rows of a given 3x3 array.

Sample Solution:

Python Code:

# Importing the NumPy library
import numpy as np

# Creating a 2D array
x = np.array([[1, 2, 3], [4, 5, 6]])

# Displaying the original array
print("Original array: ")
print(x)

# Calculating the cumulative product of all elements in the array
print("Cumulative product of the elements along a given axis:")
r = np.cumprod(x)
print(r)

# Calculating the cumulative product over rows for each of the 3 columns
print("\nProduct over rows for each of the 3 columns:")
r = np.cumprod(x, axis=0)
print(r)

# Calculating the cumulative product over columns for each of the 2 rows
print("\nProduct over columns for each of the 2 rows:")
r = np.cumprod(x, axis=1)
print(r)

Sample Output:

Original array: 
[[1 2 3]
 [4 5 6]]
Cumulative product  of the elements along a given axis:
[  1   2   6  24 120 720]

Product over rows for each of the 3 columns:
[[ 1  2  3]
 [ 4 10 18]]

Product  over columns for each of the 2 rows:
[[  1   2   6]
 [  4  20 120]]

Explanation:

In the above exercise –

x = np.array([[1,2,3], [4,5,6]]) – This line creates a 2D NumPy array x. The array has two rows and three columns.

r = np.cumprod(x) – The np.cumprod() function is then called on x with no axis specified, resulting in the cumulative product of all elements in the array. The resulting array is assigned to r.

r = np.cumprod(x,axis=0) – The np.cumprod() function is called with axis=0. This computes the cumulative product of each column, resulting in an array of the same shape as x. The resulting array is assigned to r.

r = np.cumprod(x,axis=1) – Finally, the np.cumprod() function is called with axis=1. This computes the cumulative product of each row, resulting in an array of the same shape as x. The resulting array is assigned to r.

For more Practice: Solve these Related Problems:

Implement a function that computes the cumulative product of elements in a 2D array using np.cumprod and reshapes the output.
Test the function to compute row-wise and column-wise products and verify the results with iterative multiplication.
Create a solution that returns both cumulative product and final product sums over specified axes.
Compare the np.cumprod output with a manual multiplication loop for a small matrix to ensure accuracy.

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