itermprod

Create an iterator which iteratively computes a moving product.

For a window of size W, the moving product is defined as

Installation

npm install @stdlib/stats-iter-mprod

Usage

var itermprod = require( '@stdlib/stats-iter-mprod' );

itermprod( iterator, W )

Returns an iterator which iteratively computes a moving product. The W parameter defines the number of iterated values over which to compute the moving product.

var array2iterator = require( '@stdlib/array-to-iterator' );

var arr = array2iterator( [ 2.0, 1.0, 3.0, -7.0, -5.0 ] );
var it = itermprod( arr, 3 );

// Fill the window...
var p = it.next().value; // [2.0]
// returns 2.0

p = it.next().value; // [2.0, 1.0]
// returns 2.0

p = it.next().value; // [2.0, 1.0, 3.0]
// returns 6.0

// Window begins sliding...
p = it.next().value; // [1.0, 3.0, -7.0]
// returns -21.0

p = it.next().value; // [3.0, -7.0, -5.0]
// returns 105.0

Notes

• If an iterated value is non-numeric (including NaN), the function returns NaN for at least W-1 future invocations. If non-numeric iterated values are possible, you are advised to provide an iterator which type checks and handles non-numeric values accordingly.
• As W values are needed to fill the window buffer, the first W-1 returned values are calculated from smaller sample sizes. Until the window is full, each returned value is calculated from all previously iterated values.

Examples

var runif = require( '@stdlib/random-iter-uniform' );
var itermprod = require( '@stdlib/stats-iter-mprod' );

// Create an iterator for generating uniformly distributed pseudorandom numbers:
var rand = runif( -10.0, 10.0, {
    'seed': 1234,
    'iter': 100
});

// Create an iterator for iteratively computing a moving product:
var it = itermprod( rand, 3 );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    if ( typeof v.value === 'number' ) {
        console.log( 'product: %d', v.value );
    }
}

See Also

• @stdlib/stats-iter/msum: create an iterator which iteratively computes a moving sum.
• @stdlib/stats-iter/prod: compute the product of all iterated values.

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.