Select elements using Boolean Indexing with logical operators

Last update on March 26 2025 13:11:20 (UTC/GMT +8 hours)

13. 1D Array & Boolean Indexing with Logical Operators

NumPy: Advanced Indexing Exercise-13 with Solution

Boolean Indexing with Logical Operators:

Write a NumPy program that creates a 1D NumPy array and uses boolean indexing with logical operators (e.g., & for AND, | for OR) to select elements based on multiple conditions.

Sample Solution:

Python Code:

import numpy as np

# Create a 1D NumPy array with random integers
array_1d = np.random.randint(0, 100, size=20)

# Define multiple conditions using logical operators
condition = (array_1d > 30) & (array_1d < 70) | (array_1d % 10 == 0)

# Use boolean indexing to select elements that meet the conditions
selected_elements = array_1d[condition]

# Print the original array and the selected elements
print('Original 1D array:\n', array_1d)
print('Condition (elements > 30 AND < 70 OR divisible by 10):\n', condition)
print('Selected elements:\n', selected_elements)

Output:

Original 1D array:
 [62 59 48 29 54 10 10 59 11 94 64  3 99 37 52 75 16 60 97 77]
Condition (elements > 30 AND < 70 OR divisible by 10):
 [ True  True  True False  True  True  True  True False False  True False
 False  True  True False False  True False False]
Selected elements:
 [62 59 48 54 10 10 59 64 37 52 60]

Explanation:

• Import Libraries:
• Imported numpy as np for array creation and manipulation.
• Create 1D NumPy Array:
• Create a 1D NumPy array named array_1d with random integers ranging from 0 to 99 and a length of 20.
• Define Multiple Conditions:
• Define multiple conditions using logical operators:
• Elements greater than 30 (array_1d > 30)
• Elements less than 70 (array_1d < 70)
• Elements divisible by 10 (array_1d % 10 == 0)
• Combine these conditions using & (AND) and | (OR) logical operators.
• Boolean Indexing:
• Applied boolean indexing to select elements in array_1d that meet the defined conditions.
• Print Results:
• Print the original 1D array, the boolean condition array, and the selected elements to verify the indexing operation.

For more Practice: Solve these Related Problems:

• Create a 1D array and use logical AND (&) to select elements that are both even and greater than a specified threshold.
• Write a function that uses logical OR (|) to filter an array for elements that satisfy at least one of two conditions.
• Implement a solution that combines multiple logical operators to select elements within a range and not equal to a specific value.
• Test the logical indexing on a 1D array of integers and compare the results with a loop-based filter.

Python-Numpy Code Editor:

Previous: Select Subset of elements using combined Indexing in NumPy.
Next: Select Rectangular Subarray using advanced slicing in NumPy.