NumPy: Extract first and third elements of the first and third rows from a given (4x4) array
Extract First & Third Elements of First/Third Rows
Write a NumPy program to extract the first and third elements of the first and third rows from a given (4x4) array.
Pictorial Presentation:
Sample Solution:
Python Code:
# Importing the NumPy library and aliasing it as 'np'
import numpy as np
# Creating a NumPy array 'arra_data' containing integers from 0 to 15 and reshaping it into a 4x4 matrix
arra_data = np.arange(0, 16).reshape((4, 4))
# Displaying a message indicating the original array will be printed
print("Original array:")
# Printing the original 4x4 array 'arra_data'
print(arra_data)
# Displaying a message indicating the extracted data (first and third elements of the first and third rows)
print("\nExtracted data: First and third elements of the first and third rows")
# Using slicing with a step of 2 to extract every other element in both rows and columns
print(arra_data[::2, ::2])
Sample Output:
Original array: [[ 0 1 2 3] [ 4 5 6 7] [ 8 9 10 11] [12 13 14 15]] Extracted data: First and third elements of the first and third rows [[ 0 2] [ 8 10]]
Explanation:
In the above exercise -
arra_data = np.arange(0, 16).reshape((4, 4)): This line creates a 1-dimensional NumPy array with elements from 0 to 15 (excluding 16) using np.arange(0, 16) and then reshapes it into a 2-dimensional array with 4 rows and 4 columns using .reshape((4, 4)).
print(arra_data[::2, ::2]): It prints a subarray of ‘arra_data’ by selecting every second row and every second column using the slicing syntax ::2. The : in the slicing syntax indicates selecting all elements, while the 2 after the second colon represents a step of 2, meaning every second element will be selected.
Python-Numpy Code Editor: