# y1
> Compute the [Bessel function of the second kind][bessel-second-kind] of order one.
The [Bessel function of the second kind][bessel-second-kind] of order one is defined as
## Usage
```javascript
var y1 = require( '@stdlib/math/base/special/bessely1' );
```
#### y1( x )
Computes the [Bessel function of the second kind][bessel-second-kind] of order one at `x`.
```javascript
var v = y1( 0.0 );
// returns -Infinity
v = y1( 1.0 );
// returns ~-0.781
v = y1( Infinity );
// returns 0.0
```
If `x < 0` or `x` is `NaN`, the function returns `NaN`.
```javascript
var v = y1( -1.0 );
// returns NaN
v = y1( -Infinity );
// returns NaN
v = y1( NaN );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var y1 = require( '@stdlib/math/base/special/bessely1' );
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = randu() * 10.0;
console.log( 'y1(%d) = %d', x, y1( x ) );
}
```
[bessel-second-kind]: https://en.wikipedia.org/wiki/Bessel_function#Bessel_functions_of_the_second_kind:_Y.CE.B1
