npm package: @stdlib/stats-iter-cusumabs2
Description: Create an iterator which iteratively computes a cumulative sum of squared absolute values.
Author: The Stdlib Authors
Latest version: 0.2.3

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# itercusumabs2

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

> Create an [iterator][mdn-iterator-protocol] which iteratively computes a cumulative sum of squared absolute values.

<section class="intro">

The cumulative sum of squared absolute values is defined as

<!-- <equation class="equation" label="eq:cumulative_sum_of_squared_absolute_values" align="center" raw="\begin{align*} s_0 &= x_0^2 \\ s_1 &= x_1^2 + s_0 \\ s_2 &= x_2^2 + s_1 \\ s_n &= x_n^2 + s_{n-1} = x_n^2 + \sum_{i=0}^{n-1} x_i^2 \end{align*}" alt="Equation for the cumulative sum of squared absolute values."> -->

<div class="equation" align="center" data-raw-text="\begin{align*} s_0 &amp;= x_0^2 \\ s_1 &amp;= x_1^2 + s_0 \\ s_2 &amp;= x_2^2 + s_1 \\ s_n &amp;= x_n^2 + s_{n-1} = x_n^2 + \sum_{i=0}^{n-1} x_i^2 \end{align*}" data-equation="eq:cumulative_sum_of_squared_absolute_values">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@daba99f62ed8ff3f49cf13b209c692fd9ccb6c6f/lib/node_modules/@stdlib/stats/iter/cusumabs2/docs/img/equation_cumulative_sum_of_squared_absolute_values.svg" alt="Equation for the cumulative sum of squared absolute values.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/stats-iter-cusumabs2
```

</section>

<section class="usage">

## Usage

```javascript
var itercusumabs2 = require( '@stdlib/stats-iter-cusumabs2' );
```

#### itercusumabs2( iterator )

Returns an [iterator][mdn-iterator-protocol] which iteratively computes a cumulative sum of squared absolute values.

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

var arr = array2iterator( [ 2.0, 1.0, 3.0, -7.0, -5.0 ] );
var it = itercusumabs2( arr );

var s = it.next().value;
// returns 4.0

s = it.next().value;
// returns 5.0

s = it.next().value;
// returns 14.0

s = it.next().value;
// returns 63.0

s = it.next().value;
// returns 88.0
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   If an iterated value is non-numeric (including `NaN`), the function returns `NaN` for **all** future iterations. If non-numeric iterated values are possible, you are advised to provide an [`iterator`][mdn-iterator-protocol] which type checks and handles non-numeric values accordingly.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var runif = require( '@stdlib/random-iter-uniform' );
var itercusumabs2 = require( '@stdlib/stats-iter-cusumabs2' );

// 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 cumulative sum of squared absolute values:
var it = itercusumabs2( rand );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( typeof v.value === 'number' ) {
        console.log( 'sumabs2: %d', v.value );
    }
    if ( v.done ) {
        break;
    }
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

<!-- /.references -->

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/stats-iter/cumeanabs2`][@stdlib/stats/iter/cumeanabs2]</span><span class="delimiter">: </span><span class="description">create an iterator which iteratively computes a cumulative arithmetic mean of squared absolute values.</span>
-   <span class="package-name">[`@stdlib/stats-iter/cusumabs`][@stdlib/stats/iter/cusumabs]</span><span class="delimiter">: </span><span class="description">create an iterator which iteratively computes a cumulative sum of absolute values.</span>
-   <span class="package-name">[`@stdlib/stats-iter/sumabs2`][@stdlib/stats/iter/sumabs2]</span><span class="delimiter">: </span><span class="description">compute the sum of squared absolute values for all iterated values.</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

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

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

[@stdlib/stats/iter/cumeanabs2]: https://www.npmjs.com/package/@stdlib/stats-iter-cumeanabs2

[@stdlib/stats/iter/cusumabs]: https://www.npmjs.com/package/@stdlib/stats-iter-cusumabs

[@stdlib/stats/iter/sumabs2]: https://www.npmjs.com/package/@stdlib/stats-iter-sumabs2

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