np.argmin() and np.argmax() in NumPy - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Find the index of the smallest element in a 1D array

What is the output of the following code?

NumPy

import numpy as np
arr = np.array([4, 2, 9, 1, 7])
result = np.argmin(arr)
print(result)

A 3

B 0

C 1

D 4

💡 Hint

Look for the position of the smallest number in the array.

The smallest number is 1, which is at index 3 in the array.

❓ Predict Output

intermediate

Find the index of the largest element in a 2D array flattened

What is the output of this code?

NumPy

import numpy as np
arr = np.array([[5, 12, 7], [3, 9, 15]])
result = np.argmax(arr)
print(result)

A 2

B 4

C 5

D 3

💡 Hint

np.argmax returns the index as if the array was flattened.

The largest number is 15, which is at index 5 when the array is flattened.

❓ data_output

advanced

Find indices of minimum values along axis 0

Given the array below, what is the output of np.argmin(arr, axis=0)?

NumPy

import numpy as np
arr = np.array([[8, 3, 5], [2, 7, 1], [6, 4, 9]])
result = np.argmin(arr, axis=0)
print(result)

A [2 0 2]

B [1 0 1]

C [0 1 0]

D [1 2 1]

💡 Hint

Look for the smallest value in each column.

For each column, the smallest values are at rows 1, 0, and 1 respectively.

❓ data_output

advanced

Find indices of maximum values along axis 1

What does np.argmax(arr, axis=1) return for the array below?

NumPy

import numpy as np
arr = np.array([[1, 4, 2], [9, 3, 5], [7, 8, 6]])
result = np.argmax(arr, axis=1)
print(result)

A [1 0 1]

B [2 1 0]

C [0 2 1]

D [1 2 2]

💡 Hint

Find the largest value in each row and note its index.

The largest values in each row are at indices 1, 0, and 1 respectively.

🧠 Conceptual

expert

Understanding behavior of np.argmin with multiple minimum values

Consider the array arr = np.array([3, 1, 2, 1, 4]). What index does np.argmin(arr) return and why?

A 3, because np.argmin returns the last occurrence of the minimum value

B Raises an error because there are multiple minimum values

C 2, because np.argmin returns the index of the second smallest value

D 1, because np.argmin returns the first occurrence of the minimum value

💡 Hint

Think about how np.argmin handles ties.

np.argmin returns the index of the first minimum value it finds, which is at index 1.