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# boxcox1p

> Compute a one-parameter [Box-Cox transformation][box-cox-transformation] of `1+x`.

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A one-parameter [Box-Cox transformation][box-cox-transformation] is defined as 

<!-- <equation class="equation" label="eq:boxcox_transformation_one_parameter" align="center" raw="y^{\lambda} = \begin{cases}\frac{(y + 1)^{\lambda} - 1}{\lambda} & \textrm{if}\ \lambda \neq 0 \\ \log(y + 1) & \textrm{if}\ \lambda = 0 \end{cases}" alt="One-Parameter Box-Cox Transformation"> -->

<div class="equation" align="center" data-raw-text="y^{\lambda} = \begin{cases}\frac{(y + 1)^{\lambda} - 1}{\lambda} & \textrm{if}\ \lambda \neq 0 \\ \log(y + 1) & \textrm{if}\ \lambda = 0 \end{cases}" data-equation="eq:boxcox_transformation_one_parameter">
    <img src="https://cdn.rawgit.com/stdlib-js/stdlib/cd43faf7aaac9e3059ef876713c9433ea6f3818d/lib/node_modules/@stdlib/math/base/special/boxcox1p/docs/img/equation_boxcox_transformation_one_parameter.svg" alt="One-Parameter Box-Cox Transformation" />
    <br>
</div>

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</section>

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<section class="usage">

## Usage

```javascript
var boxcox1p = require( '@stdlib/math/base/special/boxcox1p' );
```

#### boxcox1p( x, lambda )

Computes a one-parameter [Box-Cox transformation][box-cox-transformation] of `1+x`.

```javascript
var v = boxcox1p( 1.0, 2.5 );
// returns ~1.8627

v = boxcox1p( 4.0, 2.5 );
// returns ~21.9607

v = boxcox1p( 10.0, 2.5 );
// returns ~160.1246

v = boxcox1p( 2.0, 0.0 );
// returns ~1.0986

v = boxcox1p( -1.0, 2.5 );
// returns -0.4

v = boxcox1p( 0.0, -1.0 );
// returns 0.0

v = boxcox1p( -1.0, -1.0 );
// returns -Infinity
```

</section>

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<section class="examples">

## Examples

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

```javascript
var incrspace = require( '@stdlib/array/incrspace' );
var boxcox1p = require( '@stdlib/math/base/special/boxcox1p' );

var x = incrspace( -1.0, 10.0, 1.0 );
var l = incrspace( -0.5, 5.0, 0.5 );
var b;
var i;
var j;

for ( i = 0; i < x.length; i++ ) {
    for ( j = 0; j < l.length; j++ ) {
        b = boxcox1p( x[ i ], l[ j ] );
        console.log( 'boxcox1p(%d, %d) = %d', x[ i ], l[ j ], b );
    }
}
```

</section>

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## References

-   Box, G. E. P., and D. R. Cox. 1964. "An Analysis of Transformations." _Journal of the Royal Statistical Society. Series B (Methodological)_ 26 (2). \[Royal Statistical Society, Wiley]: 211–52. <http://www.jstor.org/stable/2984418>.

</section>

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<section class="links">

[box-cox-transformation]: https://en.wikipedia.org/wiki/Power_transform#Box-Cox_transformation

</section>

<!-- /.links -->
