# itermrange
> Create an [iterator][mdn-iterator-protocol] which iteratively computes a moving [range][range].
The [**range**][range] is defined as the difference between the maximum and minimum values.
## Usage
```javascript
var itermrange = require( '@stdlib/stats/iter/mrange' );
```
#### itermrange( iterator, W )
Returns an [iterator][mdn-iterator-protocol] which iteratively computes a moving [range][range]. The `W` parameter defines the number of iterated values over which to compute the moving [range][range].
```javascript
var array2iterator = require( '@stdlib/array/to-iterator' );
var arr = array2iterator( [ 2.0, 1.0, 3.0, -7.0, -5.0 ] );
var it = itermrange( arr, 3 );
// Fill the window...
var v = it.next().value; // [2.0]
// returns 0.0
v = it.next().value; // [2.0, 1.0]
// returns 1.0
v = it.next().value; // [2.0, 1.0, 3.0]
// returns 2.0
// Window begins sliding...
v = it.next().value; // [1.0, 3.0, -7.0]
// returns 10.0
v = it.next().value; // [3.0, -7.0, -5.0]
// returns 10.0
```
## Notes
- If an iterated value is non-numeric (including `NaN`), the function returns `NaN` for **at least** `W-1` future invocations. 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.
- 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 previously iterated values.
## Examples
```javascript
var runif = require( '@stdlib/random/iter/uniform' );
var itermrange = require( '@stdlib/stats/iter/mrange' );
// 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 moving range:
var it = itermrange( rand, 3 );
// Perform manual iteration...
var v;
while ( true ) {
v = it.next();
if ( typeof v.value === 'number' ) {
console.log( 'range: %d', v.value );
}
if ( v.done ) {
break;
}
}
```
[range]: https://en.wikipedia.org/wiki/Range_%28statistics%29
[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol