npm package: @stdlib/stats-incr-sumprod
Description: Compute a sum of products 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>

# incrsumprod

[![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 sum of products incrementally.

<section class="intro">

The sum of products is defined as

<!-- <equation class="equation" label="eq:sum_product" align="center" raw="s = \sum_{i=0}^{n-1} x_i y_i" alt="Equation for the sum of products."> -->

<div class="equation" align="center" data-raw-text="s = \sum_{i=0}^{n-1} x_i y_i" data-equation="eq:sum_product">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@49d8cabda84033d55d7b8069f19ee3dd8b8d1496/lib/node_modules/@stdlib/stats/incr/sumprod/docs/img/equation_sum_product.svg" alt="Equation for the sum of products.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="installation">

## Installation

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

</section>

<section class="usage">

## Usage

```javascript
var incrsumprod = require( '@stdlib/stats-incr-sumprod' );
```

#### incrsumprod()

Returns an accumulator `function` which incrementally computes a sum of products.

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

#### accumulator( \[x, y] )

If provided input values `x` and `y`, the accumulator function returns an updated sum. If not provided input value `x` and `y`, the accumulator function returns the current sum.

```javascript
var accumulator = incrsumprod();

var sum = accumulator( 2.0, 3.0 );
// returns 6.0

sum = accumulator( 1.0, -1.0 );
// returns 5.0

sum = accumulator( 3.0, 4.0 );
// returns 17.0

sum = accumulator();
// returns 17.0
```

</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 large numbers, care should be taken to prevent overflow.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

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

var accumulator;
var v1;
var v2;
var i;

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

// For each simulated datum, update the sum-product...
for ( i = 0; i < 100; i++ ) {
    v1 = randu() * 100.0;
    v2 = randu() * 100.0;
    accumulator( v1, v2 );
}
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/msumprod`][@stdlib/stats/incr/msumprod]</span><span class="delimiter">: </span><span class="description">compute a moving sum of products incrementally.</span>
-   <span class="package-name">[`@stdlib/stats-incr/prod`][@stdlib/stats/incr/prod]</span><span class="delimiter">: </span><span class="description">compute a 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>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<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-sumprod

[test-image]: https://github.com/stdlib-js/stats-incr-sumprod/actions/workflows/test.yml/badge.svg?branch=v0.2.3
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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-sumprod/tree/deno
[deno-readme]: https://github.com/stdlib-js/stats-incr-sumprod/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/stats-incr-sumprod/tree/umd
[umd-readme]: https://github.com/stdlib-js/stats-incr-sumprod/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/stats-incr-sumprod/tree/esm
[esm-readme]: https://github.com/stdlib-js/stats-incr-sumprod/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/stats-incr-sumprod/blob/main/branches.md

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

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

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

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

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

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</section>

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