time-to-botec/squiggle/node_modules/@stdlib/stats/iter/cuhmean/README.md

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# itercuhmean

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

<section class="intro">

The [harmonic mean][harmonic-mean] of positive real numbers `x_0, x_1, ..., x_{n-1}` is defined as

<!-- <equation class="equation" label="eq:harmonic_mean" align="center" raw="\begin{align}H &= \frac{n}{\frac{1}{x_0} + \frac{1}{x_1} + \cdots + \frac{1}{x_{n-1}}} \\ &= \frac{n}{\sum_{i=0}^{n-1} \frac{1}{x_i}} \\ &= \biggl( \frac{\sum_{i=0}^{n-1} \frac{1}{x_i}}{n} \biggr)^{-1}\end{align}" alt="Equation for the harmonic mean."> -->

<div class="equation" align="center" data-raw-text="\begin{align}H &amp;= \frac{n}{\frac{1}{x_0} + \frac{1}{x_1} + \cdots + \frac{1}{x_{n-1}}} \\ &amp;= \frac{n}{\sum_{i=0}^{n-1} \frac{1}{x_i}} \\ &amp;= \biggl( \frac{\sum_{i=0}^{n-1} \frac{1}{x_i}}{n} \biggr)^{-1}\end{align}" data-equation="eq:harmonic_mean">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@c00986cca2dbfac62b50df74d56662f485b6d4e5/lib/node_modules/@stdlib/stats/iter/cuhmean/docs/img/equation_harmonic_mean.svg" alt="Equation for the harmonic mean.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="usage">

## Usage

```javascript
var itercuhmean = require( '@stdlib/stats/iter/cuhmean' );
```

#### itercuhmean( iterator )

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

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

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

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

v = it.next().value;
// returns ~1.33

v = it.next().value;
// returns ~1.64

v = it.next().value;
// returns ~2.02

v = it.next().value;
// returns ~2.30
```

</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 such values accordingly.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var runif = require( '@stdlib/random/iter/uniform' );
var itercuhmean = require( '@stdlib/stats/iter/cuhmean' );

// Create an iterator for generating uniformly distributed pseudorandom numbers:
var rand = runif( 0.0, 10.0, {
    'seed': 1234,
    'iter': 100
});

// Create an iterator for iteratively computing a cumulative harmonic mean:
var it = itercuhmean( rand );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( typeof v.value === 'number' ) {
        console.log( 'hmean: %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">

[harmonic-mean]: https://en.wikipedia.org/wiki/Harmonic_mean

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

</section>

<!-- /.links -->