NumPy Factorial

This tutorial will introduce the method to calculate the element-wise factorial of a NumPy array in Python.

NumPy Factorial With the factorial() Function From Scipy

Suppose we have an array that consists of numerical values and want to calculate the factorial of each element of the array. In that case, we can use the factorial() function inside the scipy package of Python. The scipy package is an external package and does not come pre-installed with the Python programming language. The command to install the scipy package is given below.

pip install scipy

The factorial() function takes the array as an argument, carries out element-wise factorial, and returns an array that contains the calculated factorials.

from scipy.special import factorial
import numpy as np

array = np.array([[1, 3, 5], [2, 4, 6]])

factorials = factorial(array)
print(factorials)

Output:

[[  1.   6. 120.]
 [  2.  24. 720.]]

In the above code, we calculated the element-wise factorial of the NumPy array array with the factorial() function inside the scipy.special package. We first created the NumPy array array with the np.array() function. We then calculated the element-wise factorial with the factorial() function and stored the output inside another NumPy array, factorials.