numpy.diag_indices() in Python

numpy.diag_indices(n, n_dim = 2) : Returns indices in order to access the elements of main diagonal of a array with minimum dimension = 2. Returns indices in the form of tuple.
to access the main diagonal of an array.

Parameters :

n : size of array, for which indices of diag elements are required along each dimension
n_dim  : [int, optional]number of dimensions.

Return :

Indices(as tuples) to access diagonal elements.

Code 1 :

 # Python Program illustrating # working of diag_indices()    import numpy as geek     # Creates a 5 X 5 array and returns indices of # main diagonal elements d = geek.diag_indices(5) print("Indices of diagnol elements as tuple : ") print(d, "\n")    array = geek.arange(16).reshape(4,4) print("Initial array : \n", array)    # Here we can manipulate diagonal elements # by accessing the diagonal elements d = geek.diag_indices(4) array[d] = 25 print("\n New array : \n", array)

Output :

Indices of diagnol elements as tuple :
(array([0, 1, 2, 3, 4]), array([0, 1, 2, 3, 4]))

Initial array :
[[ 0  1  2  3]
[ 4  5  6  7]
[ 8  9 10 11]
[12 13 14 15]]

New array :
[[25  1  2  3]
[ 4 25  6  7]
[ 8  9 25 11]
[12 13 14 25]]

Code 2 : Manipulating 2D array

 # Python Program illustrating # working of diag_indices()    import numpy as geek     # Manipulating a 2D array  d = geek.diag_indices(3, 2)    array = geek.arange(12).reshape(4, 3)    array[d] = 111 print("Manipulated array : \n", array)

Output :

Manipulated array :
[[111   1   2]
[  3 111   5]
[  6   7 111]
[  9  10  11]]

Code 3 : Manipulating 3D array

 # Python Program illustrating # working of diag_indices()    import numpy as geek     # Setting diagonal indices d = geek.diag_indices(1, 2) print("Diag indices : \n", d)    # Creating a 3D array with all ones array = geek.ones((2, 2, 2), dtype=geek.int) print("Initial array : \n", array)    # Manipulating a 3D array  array[d] = 0 print("New array : \n", array)

Output :

Diag indices :
(array(), array())
Initial array :
[[[1 1]
[1 1]]

[[1 1]
[1 1]]]
New array :
[[[0 0]
[1 1]]

[[1 1]
[1 1]]]

Note :
These codes won’t run on online-ID. Please run them on your systems to explore the working.

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