np.argmin() and np.argmax() in NumPy - Step-by-Step Execution

Concept Flow - np.argmin() and np.argmax()

Start with array

↓

Find min or max value

↓

Locate index of min or max

↓

Return index

↓

End

The functions find the smallest or largest value in an array and return its index.

Execution Sample

NumPy

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

This code finds the index of the smallest and largest values in the array.

Execution Table

Step	Action	Array State	Value Found	Index Returned
1	Start with array	[4, 2, 7, 1, 9]	-	-
2	Find minimum value	[4, 2, 7, 1, 9]	1	-
3	Find index of minimum	[4, 2, 7, 1, 9]	1	3
4	Find maximum value	[4, 2, 7, 1, 9]	9	-
5	Find index of maximum	[4, 2, 7, 1, 9]	9	4
6	Print results	-	-	3 4

💡 All values processed; indices of min and max returned.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
arr	[4, 2, 7, 1, 9]	[4, 2, 7, 1, 9]	[4, 2, 7, 1, 9]	[4, 2, 7, 1, 9]	[4, 2, 7, 1, 9]	[4, 2, 7, 1, 9]
min_index	undefined	undefined	3	3	3	3
max_index	undefined	undefined	undefined	undefined	4	4

Key Moments - 2 Insights

Why does np.argmin() return 3 instead of the minimum value 1?

np.argmin() returns the index where the minimum value is found, not the value itself. See execution_table step 3 where index 3 corresponds to value 1.

Can np.argmax() return multiple indices if the max value appears more than once?

No, np.argmax() returns the first index of the maximum value found. This is shown in execution_table step 5 where index 4 is returned for max value 9.

Visual Quiz - 3 Questions

Look at the execution table, what is the index returned by np.argmin()?

A 3

B 1

C 4

D 0

💡 Hint

Check the 'Index Returned' column at step 3 in the execution_table.

At which step does the code find the maximum value in the array?

A Step 3

B Step 2

C Step 4

D Step 5

💡 Hint

Look at the 'Action' column in execution_table where 'Find maximum value' is listed.

If the array was [4, 9, 7, 1, 9], what would np.argmax() return?

A 0

B 1

C 4

D 3

💡 Hint

np.argmax() returns the first index of the max value; check variable_tracker for max_index behavior.

Concept Snapshot

np.argmin(array) returns the index of the smallest value.
np.argmax(array) returns the index of the largest value.
Both return the first occurrence if duplicates exist.
Useful to find positions, not values.
Input is a numpy array; output is an integer index.

Full Transcript

This lesson shows how np.argmin() and np.argmax() work by finding the index of the smallest and largest values in a numpy array. We start with an array, find the min and max values, then locate their positions. The functions return the index, not the value itself. If there are duplicates, the first index is returned. The example array is [4, 2, 7, 1, 9]. np.argmin() returns 3 because the smallest value 1 is at index 3. np.argmax() returns 4 because the largest value 9 is at index 4. This helps us quickly find where important values are in data.