@stdlib/ndarray-base-transpose NPM

transpose

Transpose a matrix (or a stack of matrices).

Installation

npm install @stdlib/ndarray-base-transpose

Usage

var transpose = require( '@stdlib/ndarray-base-transpose' );

transpose( x )

Transposes a matrix (or a stack of matrices) x.

var array = require( '@stdlib/ndarray-array' );

var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ] );
// returns <ndarray>

var sh = x.shape;
// returns [ 2, 3 ]

var y = transpose( x );
// returns <ndarray>

sh = y.shape;
// returns [ 3, 2 ]

var bool = ( x.data === y.data );
// returns true

bool = ( x.get( 0, 1 ) === y.get( 1, 0 ) );
// returns true

Notes

The returned ndarray is a view of the input ndarray. Accordingly, writing to the original ndarray will mutate the returned ndarray and vice versa. While powerful, this can lead to subtle bugs. In general, one should handle the returned ndarray as read-only.
If provided an ndarray with fewer than two dimensions, the function raises an exception.

Examples

var Float64Array = require( '@stdlib/array-float64' );
var ndarray = require( '@stdlib/ndarray-ctor' );
var rpad = require( '@stdlib/string-right-pad' );
var transpose = require( '@stdlib/ndarray-base-transpose' );

function print( arr, name ) {
    var str;
    var sh;
    var p;
    var i;
    var j;
    var k;

    sh = arr.shape;
    for ( i = 0; i < sh[0]; i++ ) {
        str = name+'['+i+',:,:] = [ ';
        p = str.length + 1;
        for ( j = 0; j < sh[1]; j++ ) {
            if ( j > 0 ) {
                str += rpad( '\n', p, ' ' );
            }
            for ( k = 0; k < sh[2]; k++ ) {
                str += arr.get( i, j, k );
                if ( k < sh[2]-1 ) {
                    str += ', ';
                }
            }
        }
        console.log( str + ' ]\n' );
    }
}

// Create a data buffer:
var buf = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

// Create a stack of matrices:
var x = new ndarray( 'float64', buf, [ 2, 2, 3 ], [ 0, 3, 1 ], 0, 'row-major' );

// Transpose the stack of matrices:
var y = transpose( x );

// Print the stacks:
console.log( '' );
print( x, 'X' );
console.log( '' );
print( y, 'Y' );

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.