@stdlib/ndarray-sub2ind v0.2.1
sub2ind
Convert subscripts to a linear index.
Installation
npm install @stdlib/ndarray-sub2ind
Usage
var sub2ind = require( '@stdlib/ndarray-sub2ind' );
sub2ind( shape, ...subscripts[, options] )
Converts subscripts to a linear index.
var shape = [ 2, 2 ];
var idx = sub2ind( shape, 1, 0 );
// returns 2
The function supports the following options
:
mode: specifies how to handle subscripts which exceed array dimensions. The following modes are supported:
throw
: specifies that the function should throw an error when a subscript exceeds array dimensions.normalize
: specifies that the function should normalize negative subscripts and throw an error when a subscript exceeds array dimensions.wrap
: specifies that the function should wrap around subscripts exceeding array dimensions using modulo arithmetic.clamp
: specifies that the function should set subscripts exceeding array dimensions to either0
(minimum index) or the maximum index along a particular dimension.
If provided a
mode
array, each array element corresponds to a dimension. If provided fewer modes than dimensions, the function reuses modes using modulo arithmetic. Default:[ 'throw' ]
.order: specifies whether an array is
row-major
(C-style) orcolumn-major
(Fortran-style). Default:'row-major'
.
By default, the function assumes a row-major array. To return a linear index for a column-major array, set the order
option.
var shape = [ 2, 2 ];
var opts = {};
opts.order = 'column-major';
var idx = sub2ind( shape, 1, 0, opts );
// returns 1
By default, the function throws an error
if provided subscripts which exceed array dimensions. To specify alternative behavior, set the mode
option.
var shape = [ 2, 2 ];
var opts = {};
opts.mode = 'wrap';
var idx = sub2ind( shape, -2, 0, opts );
// returns 0
opts.mode = 'clamp';
idx = sub2ind( shape, 10, 10, opts );
// returns 3
To specify separate modes for each dimension, provide a mode
array.
var shape = [ 2, 2, 2 ];
var opts = {
'mode': [
'wrap',
'clamp'
]
};
var idx = sub2ind( shape, -2, 10, -1, opts );
// returns 3
Examples
var numel = require( '@stdlib/ndarray-base-numel' );
var sub2ind = require( '@stdlib/ndarray-sub2ind' );
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:' );
console.log( '' );
var slice;
var idx;
var row;
var j;
var k;
for ( k = 0; k < shape[ 2 ]; k++ ) {
slice = 'A[:,:,'+k+'] = ';
console.log( slice );
for ( i = 0; i < shape[ 0 ]; i++ ) {
row = ' ';
for ( j = 0; j < shape[ 1 ]; j++ ) {
idx = sub2ind( shape, i, j, k, opts );
row += arr[ idx ];
if ( j < shape[ 1 ]-1 ) {
row += ', ';
}
}
console.log( row );
}
console.log( '' );
}
See Also
@stdlib/ndarray-array
: multidimensional arrays.@stdlib/ndarray-ctor
: multidimensional array constructor.@stdlib/ndarray-ind2sub
: convert a linear index to an array of subscripts.
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 © 2016-2024. The Stdlib Authors.