NumPy: Get the n largest values of an array
16. n Largest Values in Array
Write a NumPy program to get the n largest values of an array.
Sample Solution:
Python Code:
# Importing the NumPy library as np
import numpy as np
# Creating an array 'x' containing numbers from 0 to 9 using arange() function
x = np.arange(10)
# Displaying the original array 'x'
print("Original array:")
print(x)
# Shuffling the elements in array 'x'
np.random.shuffle(x)
# Selecting the 'n' largest elements in 'x' using argsort and slicing
n = 1
print(x[np.argsort(x)[-n:]])
Sample Output:
Original array: [0 1 2 3 4 5 6 7 8 9] [9]
Explanation:
In the above exercise –
x = np.arange(10): This statement generates a 1D array of integers from 0 to 9 (inclusive).
np.random.shuffle(x): This statement shuffles the elements of the array x in-place (i.e., the original array is modified) in a random order.
n = 1: This statement sets the variable n to 1, which represents the number of largest elements we want to extract from the shuffled array.
x[np.argsort(x)[-n:]]: This statement sorts the indices of the shuffled array x using np.argsort(x) in ascending order. Then, by slicing [-n:], we get the last n indices corresponding to the n largest elements in the array. In this case, since n = 1, the slice returns the index of the largest element in the shuffled array.
print(x[np.argsort(x)[-n:]]): Finally print() function prints the largest element in the shuffled array by indexing the array x with the calculated slice.
Pictorial Presentation:
For more Practice: Solve these Related Problems:
- Write a function that extracts the n largest elements from a 1D array using np.partition and sorts them in descending order.
- Create a solution that returns both the n largest values and their original indices.
- Implement an algorithm that finds the n largest elements without using built-in functions and compares the results.
- Test the function on arrays with duplicate values to ensure that the n largest unique values are correctly identified.
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Python-Numpy Code Editor:
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