time-to-botec/js/node_modules/@stdlib/stats/iter/cusum/README.md

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# itercusum

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

<section class="intro">

The cumulative sum is defined as

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

<div class="equation" align="center" data-raw-text="\begin{align*} s_0 &amp;= x_0 \\ s_1 &amp;= x_1 + s_0 \\ s_2 &amp;= x_2 + s_1 \\ s_n &amp;= x_n + s_{n-1} = x_n + \sum_{i=0}^{n-1} x_i \end{align*}" data-equation="eq:cumulative_sum">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@755a26b39bb6429f6d0b6dd8d13bd0bd1ec5ba35/lib/node_modules/@stdlib/stats/iter/cusum/docs/img/equation_cumulative_sum.svg" alt="Equation for the cumulative sum.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="usage">

## Usage

```javascript
var itercusum = require( '@stdlib/stats/iter/cusum' );
```

#### itercusum( iterator )

Returns an [iterator][mdn-iterator-protocol] which iteratively computes a cumulative sum.

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

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

var s = it.next().value;
// returns 2.0

s = it.next().value;
// returns 3.0

s = it.next().value;
// returns 6.0

s = it.next().value;
// returns -1.0

s = it.next().value;
// returns -6.0
```

</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 itercusum = require( '@stdlib/stats/iter/cusum' );

// 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:
var it = itercusum( rand );

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

</section>

<!-- /.examples -->

<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="references">

</section>

<!-- /.references -->

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

<section class="links">

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

</section>

<!-- /.links -->