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Module « numpy »

Fonction triu_indices_from - module numpy

Signature de la fonction triu_indices_from

def triu_indices_from(arr, k=0) 

Description

help(numpy.triu_indices_from)

Return the indices for the upper-triangle of arr.

See `triu_indices` for full details.

Parameters
----------
arr : ndarray, shape(N, N)
    The indices will be valid for square arrays.
k : int, optional
    Diagonal offset (see `triu` for details).

Returns
-------
triu_indices_from : tuple, shape(2) of ndarray, shape(N)
    Indices for the upper-triangle of `arr`.

Examples
--------
>>> import numpy as np

Create a 4 by 4 array

>>> a = np.arange(16).reshape(4, 4)
>>> a
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

Pass the array to get the indices of the upper triangular elements.

>>> triui = np.triu_indices_from(a)
>>> triui
(array([0, 0, 0, 0, 1, 1, 1, 2, 2, 3]), array([0, 1, 2, 3, 1, 2, 3, 2, 3, 3]))

>>> a[triui]
array([ 0,  1,  2,  3,  5,  6,  7, 10, 11, 15])

This is syntactic sugar for triu_indices().

>>> np.triu_indices(a.shape[0])
(array([0, 0, 0, 0, 1, 1, 1, 2, 2, 3]), array([0, 1, 2, 3, 1, 2, 3, 2, 3, 3]))

Use the `k` parameter to return the indices for the upper triangular array
from the k-th diagonal.

>>> triuim1 = np.triu_indices_from(a, k=1)
>>> a[triuim1]
array([ 1,  2,  3,  6,  7, 11])


See Also
--------
triu_indices, triu, tril_indices_from

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