fr/fr_env/lib/python3.8/site-packages/skimage/util/unique.py

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2021-02-17 12:26:31 +05:30
import numpy as np
def unique_rows(ar):
"""Remove repeated rows from a 2D array.
In particular, if given an array of coordinates of shape
(Npoints, Ndim), it will remove repeated points.
Parameters
----------
ar : 2-D ndarray
The input array.
Returns
-------
ar_out : 2-D ndarray
A copy of the input array with repeated rows removed.
Raises
------
ValueError : if `ar` is not two-dimensional.
Notes
-----
The function will generate a copy of `ar` if it is not
C-contiguous, which will negatively affect performance for large
input arrays.
Examples
--------
>>> ar = np.array([[1, 0, 1],
... [0, 1, 0],
... [1, 0, 1]], np.uint8)
>>> unique_rows(ar)
array([[0, 1, 0],
[1, 0, 1]], dtype=uint8)
"""
if ar.ndim != 2:
raise ValueError("unique_rows() only makes sense for 2D arrays, "
"got %dd" % ar.ndim)
# the view in the next line only works if the array is C-contiguous
ar = np.ascontiguousarray(ar)
# np.unique() finds identical items in a raveled array. To make it
# see each row as a single item, we create a view of each row as a
# byte string of length itemsize times number of columns in `ar`
ar_row_view = ar.view('|S%d' % (ar.itemsize * ar.shape[1]))
_, unique_row_indices = np.unique(ar_row_view, return_index=True)
ar_out = ar[unique_row_indices]
return ar_out