# spence
> [Spence’s function][spence], also known as the dilogarithm.
The dilogarithm is defined as
or also alternatively as
## Usage
```javascript
var spence = require( '@stdlib/math/base/special/spence' );
```
#### spence( x )
Evaluates [Spence’s function][spence], which is alternatively known as the dilogarithm.
```javascript
var v = spence( 3.0 );
// returns ~-1.437
v = spence( 0.0 );
// returns ~1.645
v = spence( NaN );
// returns NaN
```
For negative numbers, the dilogarithm is **not** defined.
```javascript
var v = spence( -4.0 );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var spence = require( '@stdlib/math/base/special/spence' );
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = randu() * 100.0;
console.log( 'spence( %d ) = %d', x, spence( x ) );
}
```
[spence]: https://en.wikipedia.org/wiki/Spence%27s_function
