# log1pexp
> Evaluates the [natural logarithm][@stdlib/math/base/special/ln] of `1+exp(x)`.
## Usage
```javascript
var log1pexp = require( '@stdlib/math/base/special/log1pexp' );
```
#### log1pexp( x )
Evaluates the [natural logarithm][@stdlib/math/base/special/ln] of `1+exp(x)`.
```javascript
var y = log1pexp( -10.0 );
// returns ~0.000045
y = log1pexp( 0.0 );
// returns ~0.693147
y = log1pexp( 5.0 );
// returns ~5.006715
y = log1pexp( 34.0 );
// returns 34.0
y = log1pexp( NaN );
// returns NaN
```
## Examples
```javascript
var incrspace = require( '@stdlib/array/incrspace' );
var log1pexp = require( '@stdlib/math/base/special/log1pexp' );
var x = incrspace( -10.0, 10.0, 0.01 );
var v;
var i;
for ( i = 0; i < x.length; i++ ) {
v = log1pexp( x[ i ] );
console.log( 'x: %d, f(x): %d', x[ i ], v );
}
```
[@stdlib/math/base/special/ln]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/ln