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Find Maximum value in Masked NumPy array ignoring Masked elements

NumPy: Masked Arrays Exercise-10 with Solution

Write a NumPy program to create a masked array and find the maximum value, ignoring the masked elements.

Sample Solution:

Python Code:

import numpy as np
import numpy.ma as ma

# Create a 2D NumPy array of shape (4, 4) with random integers
array_2d = np.random.randint(0, 100, size=(4, 4))

# Define the condition to mask elements greater than 50
condition = array_2d > 50

# Create a masked array from the 2D array using the condition
masked_array = ma.masked_array(array_2d, mask=condition)

# Find the maximum value in the masked array, ignoring the masked elements
max_value = masked_array.max()

# Print the original array, the masked array, and the maximum value
print('Original 2D array:\n', array_2d)
print('Masked array (elements > 50 are masked):\n', masked_array)
print('Maximum value (ignoring masked elements):', max_value)

Output:

Original 2D array:
 [[ 5  8 65 37]
 [18 63 62 93]
 [65 92 48 17]
 [32  8  1 13]]
Masked array (elements > 50 are masked):
 [[5 8 -- 37]
 [18 -- -- --]
 [-- -- 48 17]
 [32 8 1 13]]
Maximum value (ignoring masked elements): 48

Explanation:

  • Import Libraries:
    • Imported numpy as "np" for array creation and manipulation.
    • Imported numpy.ma as "ma" for creating and working with masked arrays.
  • Create 2D NumPy Array:
    • Create a 2D NumPy array named 'array_2d' with random integers ranging from 0 to 99 and a shape of (4, 4).
  • Define Condition:
    • Define a condition to mask elements in the array that are greater than 50.
  • Create Masked Array:
    • Create a masked array from the 2D array using ma.masked_array, applying the condition as the mask. Elements greater than 50 are masked.
  • Find Maximum Value:
    • Use the max method of the masked array to find the maximum value, ignoring the masked elements.
  • Print the original 2D array, the masked array, and the maximum value, ignoring the masked elements.

Python-Numpy Code Editor: