Numpy – Get Index of Max Value in Array

The Numpy library in Python comes with a number of useful built-in functions to work with and manipulate Numpy arrays. In this tutorial, we will look at how to get the index of the max value in a Numpy array with the help of some examples.

How to get the index of the maximum value in a Numpy array?

You can use the Numpy argmax() function to get the index of the max value in a Numpy array. The following is the syntax –

# get index of max value in numpy array
ar.argmax()

It returns the index corresponding to the maximum value in the array.

You can apply this function on higher dimension (greater than 1) Numpy arrays well and specify the axis along which you want to compute the maximum.

Steps to get the index of the maximum value in Numpy

Let’s now look at a step-by-step example of using the above syntax –

Step 1 – Create a Numpy array

First, we will create a Numpy array that we will be using throughout this tutorial. You can use the numpy.array() function to create Numpy array in Python.

import numpy as np

# create numpy array
ar = np.array([1, 2, 5, 3, 4])
# display the array
print(ar)

Output:

[1 2 5 3 4]

Here, we create a Numpy array with some integer values. You can see that the maximum value in the above array is 5 which occurs at index 2.

Step 2 – Find the index of the max value

Use the Numpy argmax() function to compute the index of the maximum value in the above array.

# get index of max value in array
print(ar.argmax())

Output:

2

We get 2 as the index of the maximum value in the array which is the correct answer.

If the max value occurs at multiple indices in the array, the argmax() function will return the index of the first occurrence of the max value. Let’s look at an example.

# create numpy array
ar = np.array([1, 2, 5, 3, 5, 4])
# get index of max value in array
print(ar.argmax())

Output:

2

Here, the maximum value in the array (5) occurs at the indices 2 and 4 in the above array. The argmax() function returns the index of the maximum value as 2, which is the index of the first occurrence of the maximum value in the array.

You might also be interested in –

• Numpy – Remove Duplicates From Array
• Check If Two Numpy Arrays are Equal