Python:NumPy argmin()

The ndarray.argmin() method returns the index of the minimum value in a NumPy array. The search can be performed on the flattened array or along a specified axis, and the result reflects where the smallest element appears rather than the value itself.

Syntax

ndarray.argmin(axis=None, out=None, *, keepdims=False)

Parameters:

• axis (optional): Axis along which to find the minimum index.
  • None (default): Searches the entire flattened array.
  • 0: Searches column-wise
  • 1: Searches row-wise
• out (optional): Output array that receives the result. Must have the appropriate shape.
• keepdims (optional): If True, the reduced axes are kept with size 1, preserving the dimension structure.

Return value:

An integer or array of integers representing the indices of the minimum values.

Example 1: Finding the Minimum Index in a 1D Array

In this example, the smallest number in the array is identified, and its index is returned:

import numpy as np

arr = np.array([12, 5, 7, 3, 9])
idx = arr.argmin()
print(idx)

Copy to clipboard
Copy to clipboard

The output of this code is:

3

Copy to clipboard
Copy to clipboard

Example 2: Finding Minimum Indices Along Rows

In this example, argmin() is applied along axis=1, so each row returns the index of its smallest element:

import numpy as np

arr = np.array([[4, 9, 1],
                [8, 3, 6]])

idx = arr.argmin(axis=1)
print(idx)

Copy to clipboard
Copy to clipboard

The output of this code is:

[2 1]

Copy to clipboard
Copy to clipboard

Codebyte Example

In this example, the minimum index is found both in the flattened array and along each column to show how the output changes with the axis parameter:

Visit us
Visit us
Hide code
Code
Output
Hide output
Copy to your clipboard
Copy Codebyte
Run

Frequently Asked Questions

1. What does NumPy argmin() do?

NumPy’s argmin() returns the index location of the smallest element inside an array. Instead of giving the minimum value, it identifies where that value appears, which is essential for position-based analysis.

2. What is the difference between argmin() and nanargmin()?

argmin() considers all values, including NaNs, while nanargmin() ignores NaNs and returns the index of the smallest non-NaN value.

3. What is the difference between argmin() and min() in Python?

min() (or ndarray.min()) returns the smallest value itself, while argmin() returns the index where that value occurs. One answers “what is the smallest value”, and the other answers “where is that smallest value located”.