@stdlib/stats/incr/mmidrange/README.md

Standard library statistical functions.

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# incrmmidrange

> Compute a moving [mid-range][mid-range] incrementally.

<section class="intro">

The [**mid-range**][mid-range], or **mid-extreme**, is the arithmetic mean of maximum and minimum values. Accordingly, the [mid-range][mid-range] is the midpoint of the [range][range] and a measure of central tendency.

</section>

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<section class="usage">

## Usage

```javascript
var incrmmidrange = require( '@stdlib/stats/incr/mmidrange' );
```

#### incrmmidrange( window )

Returns an accumulator `function` which incrementally computes a moving [mid-range][mid-range]. The `window` parameter defines the number of values over which to compute the moving [mid-range][mid-range].

```javascript
var accumulator = incrmmidrange( 3 );
```

#### accumulator( \[x] )

If provided an input value `x`, the accumulator function returns an updated [mid-range][mid-range]. If not provided an input value `x`, the accumulator function returns the current [mid-range][mid-range].

```javascript
var accumulator = incrmmidrange( 3 );

var mr = accumulator();
// returns null

// Fill the window...
mr = accumulator( 2.0 ); // [2.0]
// returns 2.0

mr = accumulator( 1.0 ); // [2.0, 1.0]
// returns 1.5

mr = accumulator( 3.0 ); // [2.0, 1.0, 3.0]
// returns 2.0

// Window begins sliding...
mr = accumulator( -7.0 ); // [1.0, 3.0, -7.0]
// returns -2.0

mr = accumulator( -5.0 ); // [3.0, -7.0, -5.0]
// returns -2.0

mr = accumulator();
// returns -2.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   Input values are **not** type checked. If provided `NaN`, the accumulated value is `NaN` for **at least** `W-1` 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.
-   As `W` values are needed to fill the window buffer, the first `W-1` returned values are calculated from smaller sample sizes. Until the window is full, each returned value is calculated from all provided values.

</section>

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<section class="examples">

## Examples

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

```javascript
var randu = require( '@stdlib/random/base/randu' );
var incrmmidrange = require( '@stdlib/stats/incr/mmidrange' );

var accumulator;
var v;
var i;

// Initialize an accumulator:
accumulator = incrmmidrange( 5 );

// For each simulated datum, update the moving mid-range...
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/mmean`][@stdlib/stats/incr/mmean]</span><span class="delimiter">: </span><span class="description">compute a moving arithmetic mean incrementally.</span>
-   <span class="package-name">[`@stdlib/stats/incr/mmax`][@stdlib/stats/incr/mmax]</span><span class="delimiter">: </span><span class="description">compute a moving maximum incrementally.</span>
-   <span class="package-name">[`@stdlib/stats/incr/mmin`][@stdlib/stats/incr/mmin]</span><span class="delimiter">: </span><span class="description">compute a moving minimum incrementally.</span>
-   <span class="package-name">[`@stdlib/stats/incr/mrange`][@stdlib/stats/incr/mrange]</span><span class="delimiter">: </span><span class="description">compute a moving range incrementally.</span>

</section>

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<section class="links">

[range]: https://en.wikipedia.org/wiki/Range_%28statistics%29

[mid-range]: https://en.wikipedia.org/wiki/Mid-range

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

[@stdlib/stats/incr/mmean]: https://github.com/stdlib-js/stats/tree/main/incr/mmean

[@stdlib/stats/incr/mmax]: https://github.com/stdlib-js/stats/tree/main/incr/mmax

[@stdlib/stats/incr/mmin]: https://github.com/stdlib-js/stats/tree/main/incr/mmin

[@stdlib/stats/incr/mrange]: https://github.com/stdlib-js/stats/tree/main/incr/mrange

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

</section>

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