Subtract 1D array from 2D array using NumPy Broadcasting

Last update on March 26 2025 13:15:57 (UTC/GMT +8 hours)

2. Row-wise Subtraction Using Broadcasting

Write a NumPy program that creates a 2D array x of shape (3, 4) and a 1D array y of shape (4,). Subtract y from each row of x using broadcasting.

Sample Solution:

Python Code:

# Import the NumPy library
import numpy as np

# Create a 2D array x with shape (3, 4)
x = np.array([[5, 6, 7, 8], [1, 2, 3, 4], [9, 10, 11, 12]])

# Create a 1D array y with shape (4,)
y = np.array([1, 2, 3, 4])

# Subtract y from each row of x using broadcasting
result = x - y

# Print the original arrays and the result
print("2D Array x:\n", x)
print("1D Array y:\n", y)
print("Result of x - y:\n", result)

Output:

2D Array x:
 [[ 5  6  7  8]
 [ 1  2  3  4]
 [ 9 10 11 12]]
1D Array y:
 [1 2 3 4]
Result of x - y:
 [[4 4 4 4]
 [0 0 0 0]
 [8 8 8 8]]

Explanation:

• Import NumPy library: This step imports the NumPy library, essential for numerical operations.
• Create a 2D array x: We use np.array to create a 2D array x with shape (3, 4) and elements [[5, 6, 7, 8], [1, 2, 3, 4], [9, 10, 11, 12]].
• Create a 1D array y: We use np.array to create a 1D array y with shape (4,) and elements [1, 2, 3, 4].
• Subtract y from each row of x using broadcasting: NumPy automatically adjusts the shape of y to match each row of x and performs element-wise subtraction.
• Print the original arrays and the result: This step prints the original 2D array x, the 1D array y, and the result of the subtraction.

For more Practice: Solve these Related Problems:

• Create a 2D array and subtract a 1D array from each row by reshaping the 1D array appropriately.
• Implement a function that subtracts the mean of each row from the row itself using broadcasting.
• Write a solution that subtracts a 1D array from each row of a 2D array and then computes the absolute differences.
• Test row-wise subtraction on arrays with negative values to ensure the broadcasting behaves correctly.

Python-Numpy Code Editor:

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