@stdlib/stats/base/drange/README.md

Standard library statistical functions.

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# drange

> Calculate the [range][range] of a double-precision floating-point strided array.

<section class="intro">

The [**range**][range] is defined as the difference between the maximum and minimum values.

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var drange = require( '@stdlib/stats/base/drange' );
```

#### drange( N, x, stride )

Computes the [range][range] of a double-precision floating-point strided array `x`.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, -2.0, 2.0 ] );
var N = x.length;

var v = drange( N, x, 1 );
// returns 4.0
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **x**: input [`Float64Array`][@stdlib/array/float64].
-   **stride**: index increment for `x`.

The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to compute the [range][range] of every other element in `x`,

```javascript
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var N = floor( x.length / 2 );

var v = drange( N, x, 2 );
// returns 6.0
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

<!-- eslint-disable stdlib/capitalized-comments -->

```javascript
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var N = floor( x0.length / 2 );

var v = drange( N, x1, 2 );
// returns 6.0
```

#### drange.ndarray( N, x, stride, offset )

Computes the [range][range] of a double-precision floating-point strided array using alternative indexing semantics.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, -2.0, 2.0 ] );
var N = x.length;

var v = drange.ndarray( N, x, 1, 0 );
// returns 4.0
```

The function has the following additional parameters:

-   **offset**: starting index for `x`.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the [range][range] for every other value in `x` starting from the second value

```javascript
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var N = floor( x.length / 2 );

var v = drange.ndarray( N, x, 2, 1 );
// returns 6.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If `N <= 0`, both functions return `NaN`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var Float64Array = require( '@stdlib/array/float64' );
var drange = require( '@stdlib/stats/base/drange' );

var x;
var i;

x = new Float64Array( 10 );
for ( i = 0; i < x.length; i++ ) {
    x[ i ] = round( (randu()*100.0) - 50.0 );
}
console.log( x );

var v = drange( x.length, x, 1 );
console.log( v );
```

</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/base/dmax`][@stdlib/stats/base/dmax]</span><span class="delimiter">: </span><span class="description">calculate the maximum value of a double-precision floating-point strided array.</span>
-   <span class="package-name">[`@stdlib/stats/base/dmin`][@stdlib/stats/base/dmin]</span><span class="delimiter">: </span><span class="description">calculate the minimum value of a double-precision floating-point strided array.</span>
-   <span class="package-name">[`@stdlib/stats/base/dnanrange`][@stdlib/stats/base/dnanrange]</span><span class="delimiter">: </span><span class="description">calculate the range of a double-precision floating-point strided array, ignoring NaN values.</span>
-   <span class="package-name">[`@stdlib/stats/base/range`][@stdlib/stats/base/range]</span><span class="delimiter">: </span><span class="description">calculate the range of a strided array.</span>
-   <span class="package-name">[`@stdlib/stats/base/srange`][@stdlib/stats/base/srange]</span><span class="delimiter">: </span><span class="description">calculate the range of a single-precision floating-point strided array.</span>

</section>

<!-- /.related -->

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

<section class="links">

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

[@stdlib/array/float64]: https://www.npmjs.com/package/@stdlib/array-float64

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

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

[@stdlib/stats/base/dmax]: https://github.com/stdlib-js/stats/tree/main/base/dmax

[@stdlib/stats/base/dmin]: https://github.com/stdlib-js/stats/tree/main/base/dmin

[@stdlib/stats/base/dnanrange]: https://github.com/stdlib-js/stats/tree/main/base/dnanrange

[@stdlib/stats/base/range]: https://github.com/stdlib-js/stats/tree/main/base/range

[@stdlib/stats/base/srange]: https://github.com/stdlib-js/stats/tree/main/base/srange

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

</section>

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