README
ind2sub
Convert a linear index to an array of subscripts.
Installation
npm install @stdlib/ndarray-ind2sub
Usage
var ind2sub = require( '@stdlib/ndarray-ind2sub' );
ind2sub( shape, idx[, options] )
Converts a linear index to an array of subscripts.
var shape = [ 2, 2 ];
var s = ind2sub( shape, 2 );
// returns [ 1, 0 ]
The function supports the following options
:
mode
: specifies how to handle a linear index which exceeds array dimensions. The following modes are supported:throw
: specifies that the function should throw an error when a linear index exceeds array dimensions.wrap
: specifies that the function should wrap around a linear index exceeding array dimensions using modulo arithmetic.clamp
: specifies that the function should set a linear index exceeding array dimensions to either0
(minimum linear index) or the maximum linear index.
order
: specifies whether an array isrow-major
(C-style) orcolumn-major
(Fortran-style). Default:'row-major'
.
By default, the function assumes a row-major array. To return subscripts for a column-major array, set the order
option.
var shape = [ 2, 2 ];
var opts = {};
opts.order = 'column-major';
var s = ind2sub( shape, 1, opts );
// returns [ 1, 0 ]
By default, the function throws an error
if provided a linear index which exceeds array dimensions. To specify alternative behavior, set the mode
option.
var shape = [ 2, 2 ];
var opts = {};
opts.mode = 'wrap';
var s = ind2sub( shape, -5, opts );
// returns [ 1, 1 ]
opts.mode = 'clamp';
s = ind2sub( shape, 7, opts );
// returns [ 1, 1 ]
ind2sub.assign( shape, idx[, options], out )
Converts a linear index to an array of subscripts and assigns results to a provided output array.
var shape = [ 2, 2 ];
var out = [ 0, 0 ];
var subscripts = ind2sub.assign( shape, 1, out );
// returns [ 0, 1 ]
var bool = ( subscripts === out );
// returns true
The function accepts the same options
as above.
Examples
var numel = require( '@stdlib/ndarray-base-numel' );
var ind2sub = require( '@stdlib/ndarray-ind2sub' );
var shape = [ 3, 3, 3 ];
var len = numel( shape );
var arr = [];
var i;
for ( i = 0; i < len; i++ ) {
arr.push( i );
}
var opts = {
'order': 'column-major'
};
console.log( '' );
console.log( 'Dimensions: %s.', shape.join( 'x' ) );
console.log( 'View (subscripts):' );
console.log( '' );
var row;
var s;
row = ' ';
for ( i = 0; i < len; i++ ) {
s = ind2sub( shape, i, opts );
row += '(' + s.join( ',' ) + ')';
if ( (i+1)%shape[0] === 0 ) {
console.log( row );
row = ' ';
} else {
row += ', ';
}
if ( (i+1)%(shape[0]*shape[1]) === 0 ) {
console.log( '' );
}
}
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
License
See LICENSE.
Copyright
Copyright © 2016-2022. The Stdlib Authors.