Cumulative Product

Computes the cumulative product of an array.

Installation

$ npm install compute-cprod

For use in the browser, use browserify.

Usage

var cprod = require( 'compute-cprod' );

cprod( arr[, options] )

Computes the cumulative product of an array. For primitive arrays,

var data = [ 1, 2, 3, 4 ];

var arr = cprod( data );
// returns [ 1, 2, 6, 24 ]

The function accepts two options:

• copy: boolean indicating whether to return a new array containing the cumulative products. Default: true.
• accessor: accessor function for accessing numeric values in object arrays.

To mutate the input array (e.g., when input values can be discarded or when optimizing memory usage), set the copy option to false.

var data = [ 1, 2, 3, 4 ];

var arr = cprod( data, {
	'copy': false
});
// returns [ 1, 2, 6, 24 ]

console.log( data === arr );
// returns true

For object arrays, provide an accessor function for accessing numeric array values.

var data = [
	['beep', 1],
	['boop', 2],
	['bap', 3],
	['baz', 4]
];

function getValue( d, i ) {
	return d[ 1 ];
}

var arr = cprod( arr, {
	'accessor': getValue
});
// returns [ 1, 2, 6, 24 ]

Note: the function returns an array with a length equal to the original input array.

Examples

var cprod = require( 'compute-cprod' );

var data = new Array( 10 );
for ( var i = 0; i < data.length; i++ ) {
	data[ i ] = Math.round( Math.random() * 10 ) + 1;
}

console.log( cprod( data ) );
// returns [...]

To run the example code from the top-level application directory,

$ node ./examples/index.js

Tests

Unit

Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

License

MIT license.

Copyright

Copyright © 2015. Philipp Burckhardt.