NumPy: Calculate the sum of all columns of a 2D NumPy array
Sum all columns of a 2D array.
Write a NumPy program to calculate the sum of all columns in a 2D NumPy array.
Sample Solution:
Python Code:
# Importing the NumPy library and aliasing it as 'np'
import numpy as np
# Generating a NumPy array 'num' containing numbers from 0 to 35 using arange()
num = np.arange(36)
# Reshaping the array 'num' into a 4x9 matrix and assigning it to 'arr1'
arr1 = np.reshape(num, [4, 9])
# Displaying a message indicating the original array will be printed
print("Original array:")
# Printing the original array 'arr1'
print(arr1)
# Computing the sum of each column of the array 'arr1' along axis 0 (columns) and storing it in 'result'
result = arr1.sum(axis=0)
# Displaying a message indicating the sum of all columns will be printed
print("\nSum of all columns:")
# Printing the sum of each column of the array 'arr1'
print(result)
Sample Output:
Original array: [[ 0 1 2 3 4 5 6 7 8] [ 9 10 11 12 13 14 15 16 17] [18 19 20 21 22 23 24 25 26] [27 28 29 30 31 32 33 34 35]] Sum of all columns: [54 58 62 66 70 74 78 82 86]
Explanation:
This above code demonstrates how to use NumPy to find the sum of elements along the columns of a 2D array.
num = np.arange(36): This code creates a 1D NumPy array called num with elements from 0 to 35.
arr1 = np.reshape(num, [4, 9]): This code reshapes the num array into a 2D array ‘arr1’ with 4 rows and 9 columns.
result = arr1.sum(axis=0): This code calculates the sum of elements along the columns (axis=0) of the 2D array ‘arr1’. The result is a 1D array with the same length as the number of columns in ‘arr1’.
Pictorial Presentation:
Python-Numpy Code Editor: