# @stdlib/ndarray-base-ind

0.2.1 • Public • Published

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# ind

Return an index given an index mode.

## Installation

npm install @stdlib/ndarray-base-ind

## Usage

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

#### ind( idx, max, mode )

Returns an index given an index mode.

var idx = ind( 2, 9, 'throw' );
// returns 2

idx = ind( -1, 9, 'throw' );
// throws <RangeError>

idx = ind( 10, 9, 'throw' );
// throws <RangeError>

// Wrapping indices around using modulo arithmetic:
idx = ind( 2, 9, 'wrap' );
// returns 2

idx = ind( 10, 9, 'wrap' );
// returns 0

idx = ind( -1, 9, 'wrap' );
// returns 9

// Clamping indices to first and last indices:
idx = ind( 2, 9, 'clamp' );
// returns 2

idx = ind( 10, 9, 'clamp' );
// returns 9

idx = ind( -1, 9, 'clamp' );
// returns 0

// Normalizing negative indices:
idx = ind( 2, 9, 'normalize' );
// returns 2

idx = ind( -4, 9, 'normalize' );
// returns 6

#### ind.factory( mode )

Returns a function for returning an index according to a provided index mode.

var fcn = ind.factory( 'clamp' );

var idx = fcn( 2, 9 );
// returns 2

idx = fcn( 10, 9 );
// returns 9

idx = fcn( -1, 9 );
// returns 0

The function returns a function accepts the following arguments:

• index: input index.
• max: maximum index value.

## Notes

• Both functions support the following modes:

• throw: specifies that the function should throw an error when an index is outside the interval [0, max].
• normalize: specifies that the function should normalize negative indices and throw an error when an index is outside the interval [-max-1, max].
• wrap: specifies that the function should wrap around an index using modulo arithmetic.
• clamp: specifies that the function should set an index less than 0 to 0 (minimum index) and set an index greater than max to max.

## Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var ind = require( '@stdlib/ndarray-base-ind' );

var modes;
var mode;
var idx;
var out;
var i;

modes = [ 'clamp', 'wrap' ];

for ( i = 0; i < 100; i++ ) {
idx = discreteUniform( -20, 20 );
mode = modes[ discreteUniform( 0, modes.length-1 ) ];
out = ind( idx, 9, mode );
console.log( '%d => %s(%d,%d) => %d', idx, mode, 0, 9, out );
}

## 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.

## Package Sidebar

### Install

npm i @stdlib/ndarray-base-ind

### Repository

github.com/stdlib-js/ndarray-base-ind

stdlib.io

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