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How to scale a NumPy array?

Learn, how can we scale a NumPy array?
By Pranit Sharma Last updated : December 26, 2023

Problem statement

Suppose that we are given a numpy array of shape (n, m) and we need to scale this numpy array by a factor of k which results in an array of shapes (n*k, m*k).

That is, the value of each cell in the original array is copied into k corresponding cells in the resulting array. Assuming arbitrary array size and scaling factor, we need to find the most efficient way to do this.

Scaling a NumPy array

To scale a NumPy array, we can use numpy.kron() which is used to compute the Kronecker product of two arrays which means to create a composite array made of blocks of the second array scaled by the first.

It takes two parameters a, b which are the input arrays for which the Kronecker product is computed.

We can create an array filled with ones of shape K by which we need to scale the original array and then we can apply numpy.kron() on both arrays.

Syntax

Below is the syntax of numpy.kron() method:

numpy.kron(a, b)

Let us understand with the help of an example,

Python code to scale a numpy array

# Import numpy
import numpy as np

# Creating a numpy array
arr = np.array([[1, 1],[0, 1]])

# Display original array
print("Original array:\n",arr,"\n")

# Scaling up the original array
k = 2
res = np.kron(arr,np.ones((k,k)))

# Display result
print("Result:\n",res,"\n")

Output

In this example, we have used the following Python basic topics that you should learn:

• Python print() method
• Python data types
• Python variables
• Python NumPy

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