npm package: @stdlib/stats-incr-prod
Description: Compute a product incrementally.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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</details>

# incrprod

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Compute a product incrementally.

<section class="intro">

The product is defined as

<!-- <equation class="equation" label="eq:product" align="center" raw="p = \prod_{i=0}^{n-1} x_i" alt="Equation for the product."> -->

<div class="equation" align="center" data-raw-text="p = \prod_{i=0}^{n-1} x_i" data-equation="eq:product">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@ae1331d17d505898a27e695fc60144d786627384/lib/node_modules/@stdlib/stats/incr/prod/docs/img/equation_product.svg" alt="Equation for the product.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/stats-incr-prod
```

</section>

<section class="usage">

## Usage

```javascript
var incrprod = require( '@stdlib/stats-incr-prod' );
```

#### incrprod()

Returns an accumulator `function` which incrementally computes a product.

```javascript
var accumulator = incrprod();
```

#### accumulator( \[x] )

If provided an input value `x`, the accumulator function returns an updated product. If not provided an input value `x`, the accumulator function returns the current product.

```javascript
var accumulator = incrprod();

var prod = accumulator( 2.0 );
// returns 2.0

prod = accumulator( 1.0 );
// returns 2.0

prod = accumulator( 3.0 );
// returns 6.0

prod = accumulator();
// returns 6.0
```

Under certain conditions, overflow may be transient.

```javascript
// Large values:
var x = 5.0e+300;
var y = 1.0e+300;

// Tiny value:
var z = 2.0e-302;

// Initialize an accumulator:
var accumulator = incrprod();

var prod = accumulator( x );
// returns 5.0e+300

// Transient overflow:
prod = accumulator( y );
// returns Infinity

// Recover a finite result:
prod = accumulator( z );
// returns 1.0e+299
```

Similarly, under certain conditions, underflow may be transient.

```javascript
// Tiny values:
var x = 4.0e-302;
var y = 9.0e-303;

// Large value:
var z = 2.0e+300;

// Initialize an accumulator:
var accumulator = incrprod();

var prod = accumulator( x );
// returns 4.0e-302

// Transient underflow:
prod = accumulator( y );
// returns 0.0

// Recover a non-zero result:
prod = accumulator( z );
// returns 7.2e-304
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   Input values are **not** type checked. If provided `NaN` or a value which, when used in computations, results in `NaN`, the accumulated value is `NaN` for **all** future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
-   For long running accumulations or accumulations of either large or small numbers, care should be taken to prevent overflow and underflow. Note, however, that overflow/underflow may be transient, as the accumulator does not use a double-precision floating-point number to store an accumulated product. Instead, the accumulator splits an accumulated product into a normalized **fraction** and **exponent** and updates each component separately. Doing so guards against a loss in precision.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random-base-randu' );
var incrprod = require( '@stdlib/stats-incr-prod' );

var accumulator;
var v;
var i;

// Initialize an accumulator:
accumulator = incrprod();

// For each simulated value, update the product...
for ( i = 0; i < 100; i++ ) {
    v = randu() * 100.0;
    accumulator( v );
}
console.log( accumulator() );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/stats-incr/mprod`][@stdlib/stats/incr/mprod]</span><span class="delimiter">: </span><span class="description">compute a moving product incrementally.</span>
-   <span class="package-name">[`@stdlib/stats-incr/sum`][@stdlib/stats/incr/sum]</span><span class="delimiter">: </span><span class="description">compute a sum incrementally.</span>
-   <span class="package-name">[`@stdlib/stats-incr/summary`][@stdlib/stats/incr/summary]</span><span class="delimiter">: </span><span class="description">compute a statistical summary incrementally.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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[npm-url]: https://npmjs.org/package/@stdlib/stats-incr-prod

[test-image]: https://github.com/stdlib-js/stats-incr-prod/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/stats-incr-prod/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/stats-incr-prod/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/stats-incr-prod?branch=main

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[stdlib]: https://github.com/stdlib-js/stdlib

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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/stats-incr-prod/tree/deno
[deno-readme]: https://github.com/stdlib-js/stats-incr-prod/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/stats-incr-prod/tree/umd
[umd-readme]: https://github.com/stdlib-js/stats-incr-prod/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/stats-incr-prod/tree/esm
[esm-readme]: https://github.com/stdlib-js/stats-incr-prod/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/stats-incr-prod/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/stats-incr-prod/main/LICENSE

<!-- <related-links> -->

[@stdlib/stats/incr/mprod]: https://www.npmjs.com/package/@stdlib/stats-incr-mprod

[@stdlib/stats/incr/sum]: https://www.npmjs.com/package/@stdlib/stats-incr-sum

[@stdlib/stats/incr/summary]: https://www.npmjs.com/package/@stdlib/stats-incr-summary

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</section>

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