NumPy: Create random vector of size 15 and replace the maximum value by -1

Last update on March 25 2025 12:21:07 (UTC/GMT +8 hours)

11. Replace Maximum in Vector with -1

Write a NumPy program to create random vector of size 15 and replace the maximum value by -1.

Sample Solution:

Python Code :

# Importing the NumPy library as np
import numpy as np

# Generating an array 'x' with 15 random floats between 0 and 1 using np.random.random()
x = np.random.random(15)

# Displaying the original array 'x'
print("Original array:")
print(x)

# Finding the index of the maximum value in the array using x.argmax()
# Replacing the maximum value with -1 using the index obtained from x.argmax()
x[x.argmax()] = -1

# Displaying the modified array where the maximum value has been replaced by -1
print("Maximum value replaced by -1:")
print(x) 

Sample Output:

Original array:                                                        
[ 0.04921181  0.83545304  0.4394982   0.81889845  0.8022234   0.46176053                                                                      
  0.95785815  0.86968759  0.35100099  0.00107607  0.4330148   0.56632168                                                                      
  0.57764716  0.09226267  0.01710047]                                  
Maximum value replaced by -1:                                          
[ 0.04921181  0.83545304  0.4394982   0.81889845  0.8022234   0.46176053                                                                      
 -1.          0.86968759  0.35100099  0.00107607  0.4330148   0.56632168                                                                      
  0.57764716  0.09226267  0.01710047]

Explanation:

In the above exercise –

x = np.random.random(15): This line creates a 1D array x with 15 random floating-point values between 0 and 1 using the np.random.random() function.

x[x.argmax()] = -1: This line first finds the index of the maximum value in the array x using the argmax() method. Then, it replaces the maximum value in the array with -1 using array indexing.

print(x): This line prints the modified array x with the maximum value replaced by -1.

When you run the code, you'll get an output similar to this (note that the actual output will vary since the array is generated randomly):

Original array:

[ 0.04921181 0.83545304 0.4394982 0.81889845 0.8022234 0.46176053

0.95785815 0.86968759 0.35100099 0.00107607 0.4330148 0.56632168

0.57764716 0.09226267 0.01710047]

Maximum value replaced by -1:

[ 0.04921181 0.83545304 0.4394982 0.81889845 0.8022234 0.46176053

-1. 0.86968759 0.35100099 0.00107607 0.4330148 0.56632168

0.57764716 0.09226267 0.01710047]

The output shows the modified array x with the maximum value replaced by -1.

Pictorial Presentation:

For more Practice: Solve these Related Problems:

• Write a function that finds the maximum value in a 1D array and replaces it with -1 using np.argmax.
• Create a solution that replaces all occurrences of the maximum value in the array with -1.
• Implement a method that verifies the new array by checking that the maximum value is no longer present.
• Test the function on arrays containing negative, zero, and positive values to ensure correctness.

Python-Numpy Code Editor: