ind2sub
Convert a linear index to an array of subscripts.
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.normalize: specifies that the function should normalize negative linear indices and 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 is
row-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( '' );
}
}