numpy.unique()

The numpy.unique() function returns unique elements from a given array or matrix. It returns the sorted unique elements of an array or matrix.

Syntax

The basic syntax of the numpy.unique() function is:

numpy.unique(arr, return_index=False, return_inverse=False, return_counts=False, axis=None)

Where arr is the input array.

Example

import numpy as np

arr = np.array([10, 20, 10, 30, 20, 40])
print(np.unique(arr))

Output:

[10 20 30 40]

In this example, the numpy.unique() function returns the unique elements in the input array arr. It should be noted that the function returns elements in a sorted order.

Explanation

The numpy.unique() function returns the unique elements from a given array or matrix. These elements are sorted in ascending order. The unique elements are determined by comparing the elements in the input array pairwise.

Use

The numpy.unique() function can be very useful when you want to find unique elements in an array or matrix. It can be used for various operations like filtering unique values, value counts, etc.

Important Points

• numpy.unique() function returns an array of unique elements.
• If the input array contains NaN values, then they are also considered while computing the unique elements.
• If we want to return the indices for the unique elements, we can set the return_index parameter as True.
• If we want to return the inverse of the input array such that each element in the original array is replaced by its index in the returned array, we can set the return_inverse parameter as True.
• If we want to return the count of each unique element in the input array, we can set the return_counts parameter as True.

Summary

The numpy.unique() function returns unique elements from an array or matrix. These elements are sorted in ascending order. The function can be used for various operations like filtering unique values, value counts, etc. The parameters like return_index, return_inverse, and return_counts can be used to return additional information like the indices for the unique elements, the inverse of the input array, and the count of each unique element in the input array.