# incrmidrange
> Compute a [mid-range][mid-range] incrementally.
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.
## Usage
```javascript
var incrmidrange = require( '@stdlib/stats/incr/midrange' );
```
#### incrmidrange()
Returns an accumulator `function` which incrementally computes a [mid-range][mid-range].
```javascript
var accumulator = incrmidrange();
```
#### 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 = incrmidrange();
var midrange = accumulator();
// returns null
midrange = accumulator( -2.0 );
// returns -2.0
midrange = accumulator( 1.0 );
// returns -0.5
midrange = accumulator( 3.0 );
// returns 0.5
midrange = accumulator();
// returns 0.5
```
## Notes
- Input values are **not** type checked. If provided `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.
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var incrmidrange = require( '@stdlib/stats/incr/midrange' );
var accumulator;
var v;
var i;
// Initialize an accumulator:
accumulator = incrmidrange();
// For each simulated datum, update the mid-range...
for ( i = 0; i < 100; i++ ) {
v = randu() * 100.0;
accumulator( v );
}
console.log( accumulator() );
```
[range]: https://en.wikipedia.org/wiki/Range_%28statistics%29
[mid-range]: https://en.wikipedia.org/wiki/Mid-range