The numpy.diag_indices() function 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.
Syntax: numpy.diag_indices(n, n_dim = 2)
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 :
Python3
# 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 diagonal 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)
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Output :
Indices of diagonal 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
# 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)
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Output :
Manipulated array : [[111 1 2] [ 3 111 5] [ 6 7 111] [ 9 10 11]]
Code 3 : Manipulating 3D array
Python
# 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)
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Output :
Diag indices : (array([0]), array([0])) 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 IDE’s. So please, run them on your systems to explore the working.