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assignDiagonal

Assign elements from a broadcasted input ndarray to a specified diagonal of an output ndarray.

For an M-by-N matrix A, the k-th diagonal is defined as

$$D_k = \{\, A_{i,j} : j - i = k \,\}$$

where k = 0 corresponds to the main diagonal, k > 0 corresponds to the super-diagonals (above the main diagonal), and k < 0 corresponds to the sub-diagonals (below the main diagonal).

Installation

npm install @stdlib/ndarray-base-assign-diagonal

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var assignDiagonal = require( '@stdlib/ndarray-base-assign-diagonal' );

assignDiagonal( arrays, dims, k )

Assigns elements from a broadcasted input ndarray to a specified diagonal of an output ndarray.

var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );
var zeros = require( '@stdlib/ndarray-zeros' );

var x = scalar2ndarray( 1.0 );
// returns <ndarray>

var y = zeros( [ 3, 3 ] );
// returns <ndarray>[ [ 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 0.0 ], [ 0.0, 0.0, 0.0 ] ]

var out = assignDiagonal( [ x, y ], [ 0, 1 ], 0 );
// returns <ndarray>[ [ 1.0, 0.0, 0.0 ], [ 0.0, 1.0, 0.0 ], [ 0.0, 0.0, 1.0 ] ]

var bool = ( out === y );
// returns true

The function accepts the following arguments:

• arrays: array-like object containing one input ndarray and one output ndarray.
• dims: dimension indices defining the plane in which to assign elements to the diagonal.
• k: diagonal offset.

Notes

• The order of the dimension indices contained in dims matters. The first element specifies the row-like dimension. The second element specifies the column-like dimension.
• Each provided dimension index must reside on the interval [-ndims, ndims-1].
• The diagonal offset k is interpreted as column - row. Accordingly, when k = 0, the function assigns to the main diagonal; when k > 0, the function assigns to a diagonal above the main diagonal; and when k < 0, the function assigns to a diagonal below the main diagonal.
• The input ndarray must be broadcast compatible with the output ndarray view defined by the specified diagonal.

Examples

var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var zeros = require( '@stdlib/ndarray-zeros' );
var assignDiagonal = require( '@stdlib/ndarray-base-assign-diagonal' );

// Create a stack of matrices:
var y = zeros( [ 2, 3, 3 ] );
console.log( ndarray2array( y ) );

// Assign a scalar to each main diagonal:
assignDiagonal( [ scalar2ndarray( 1.0 ), y ], [ 1, 2 ], 0 );
console.log( ndarray2array( y ) );

// Assign a scalar to each super-diagonal:
assignDiagonal( [ scalar2ndarray( 2.0 ), y ], [ 1, 2 ], 1 );
console.log( ndarray2array( y ) );

// Assign a scalar to each sub-diagonal:
assignDiagonal( [ scalar2ndarray( 3.0 ), y ], [ 1, 2 ], -1 );
console.log( ndarray2array( y ) );

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Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.