@stdlib/ndarray-base-vind2bind NPM

vind2bind

Convert a linear index in an array view to a linear index in an underlying data buffer.

Installation

npm install @stdlib/ndarray-base-vind2bind

Usage

var vind2bind = require( '@stdlib/ndarray-base-vind2bind' );

vind2bind( shape, strides, offset, order, idx, mode )

Converts a linear index in an array view to a linear index in an underlying data buffer.

var shape = [ 3, 3 ];
var order = 'row-major';
var strides = [ -3, 1 ];
var offset = 6;

var idx = vind2bind( shape, strides, offset, order, 1, 'throw' );
// returns 7

The function supports the following modes:

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 either 0 (minimum linear index) or the maximum linear index.

var shape = [ 2, 2 ];
var order = 'row-major';
var strides = [ -2, 1 ];
var offset = 2;

var idx = vind2bind( shape, strides, offset, order, -2, 'wrap' );
// returns 0

idx = vind2bind( shape, strides, offset, order, 10, 'clamp' );
// returns 1

The order parameter specifies whether an array is row-major (C-style) or column-major (Fortran-style).

var shape = [ 2, 2 ];
var order = 'column-major';
var strides = [ 1, -2 ];
var offset = 2;

var idx = vind2bind( shape, strides, offset, order, 2, 'throw' );
// returns 0

Examples

var shape2strides = require( '@stdlib/ndarray-base-shape2strides' );
var strides2offset = require( '@stdlib/ndarray-base-strides2offset' );
var numel = require( '@stdlib/ndarray-base-numel' );
var randu = require( '@stdlib/random-base-randu' );
var vind2bind = require( '@stdlib/ndarray-base-vind2bind' );

// Specify array meta data:
var shape = [ 3, 3, 3 ];
var order = 'row-major';

// Compute array meta data:
var len = numel( shape );
var strides = shape2strides( shape, order );

// Randomly flip the sign of strides...
var i;
for ( i = 0; i < shape.length; i++ ) {
    if ( randu() < 0.5 ) {
        strides[ i ] *= -1;
    }
}

// Compute the underlying data buffer index offset:
var offset = strides2offset( shape, strides );

// Print array info:
console.log( 'Dims: %s', shape.join( 'x' ) );
console.log( 'Strides: %s', strides.join( ',' ) );
console.log( 'Offset: %d', offset );

// For each view index, determine the corresponding index into an array's underlying data buffer...
var ind;
for ( i = 0; i < len; i++ ) {
    ind = vind2bind( shape, strides, offset, order, i, 'throw' );
    console.log( 'view[%d] => buffer[%d]', i, ind );
}

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.