dask.array.tril_indices_from
dask.array.tril_indices_from¶
- dask.array.tril_indices_from(arr, k=0)[source]¶
Return the indices for the lower-triangle of arr.
This docstring was copied from numpy.tril_indices_from.
Some inconsistencies with the Dask version may exist.
See tril_indices for full details.
- Parameters
- arrarray_like
The indices will be valid for square arrays whose dimensions are the same as arr.
- kint, optional
Diagonal offset (see tril for details).
See also
Notes
New in version 1.4.0.
Examples
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 lower triangular elements.
>>> trili = np.tril_indices_from(a) >>> trili (array([0, 1, 1, 2, 2, 2, 3, 3, 3, 3]), array([0, 0, 1, 0, 1, 2, 0, 1, 2, 3]))
>>> a[trili] array([ 0, 4, 5, 8, 9, 10, 12, 13, 14, 15])
This is syntactic sugar for tril_indices().
>>> np.tril_indices(a.shape[0]) (array([0, 1, 1, 2, 2, 2, 3, 3, 3, 3]), array([0, 0, 1, 0, 1, 2, 0, 1, 2, 3]))
Use the k parameter to return the indices for the lower triangular array up to the k-th diagonal.
>>> trili1 = np.tril_indices_from(a, k=1) >>> a[trili1] array([ 0, 1, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15])