NumPy: Change the sign of a given array to that of a given array, element-wise

Last update on March 25 2025 12:21:20 (UTC/GMT +8 hours)

37. Copy Sign from One Array to Another

Write a NumPy program to change the sign of a given array to that of a given array, element-wise.

Sample Solution:

Python Code:

# Importing the NumPy library
import numpy as np

# Creating an array with integer values from -1 to 2
x1 = np.array([-1, 0, 1, 2])

# Displaying the original array x1
print("Original array: ")
print(x1)

# Assigning a floating-point value to x2
x2 = -2.1

# Displaying the sign of x1 with respect to x2, element-wise using np.copysign()
print("\nSign of x1 to that of x2, element-wise:")
print(np.copysign(x1, x2)) 

Sample Output:

Original array: 
[-1  0  1  2]

Sign of x1 to that of x2, element-wise:
[-1. -0. -1. -2.]

Explanation:

x1 = np.array([-1, 0, 1, 2]): x1 is a 1-dimensional NumPy array of integers, with the values [-1, 0, 1, 2].

x2 = -2.1: x2 is a scalar value of type float.

np.copysign(x1, x2): This code returns an array with the same magnitude as x1, but with the sign of x2, which is negative. Therefore, the output will be array([-1. -0. -1. -2.]), which is an array with the same magnitude as x1, but with the sign changed to negative.

For more Practice: Solve these Related Problems:

• Implement a function that uses np.copysign to assign the sign of one array to the magnitude of another.
• Test the function on two arrays of equal length and verify that the result has the sign of the second array.
• Create a solution that handles cases where one of the arrays contains zeros or negative values.
• Compare the output of np.copysign with manual element-wise conditional assignments for validation.

Python-Numpy Code Editor:

Next: Write a NumPy program to compute numerical negative value for all elements in a given array.