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numpy.unique_inverse

numpy.unique_inverse(x)[source]

Find the unique elements of x and indices to reconstruct x.

This function is an Array API compatible alternative to:

np.unique(x, return_inverse=True, equal_nan=False, sorted=False)

but returns a namedtuple for easier access to each output.

Note

This function currently always returns a sorted result, however, this could change in any NumPy minor release.

Parameters:
xarray_like

Input array. It will be flattened if it is not already 1-D.

Returns:
outnamedtuple

The result containing:

  • values - The unique elements of an input array.
  • inverse_indices - The indices from the set of unique elements that reconstruct x.

See also

unique

Find the unique elements of an array.

Examples

>>> import numpy as np
>>> x = [1, 1, 2]
>>> uniq = np.unique_inverse(x)
>>> uniq.values
array([1, 2])
>>> uniq.inverse_indices
array([0, 0, 1])

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https://numpy.org/doc/2.4/reference/generated/numpy.unique_inverse.html