# drotg
> Construct a Givens plane rotation.
## Usage
```javascript
var drotg = require( '@stdlib/blas/base/drotg' );
```
#### drotg( a, b )
Constructs a Givens plane rotation provided two double-precision floating-point values `a` and `b`.
```javascript
var out = drotg( 0.0, 2.0 );
// returns [ 2.0, 1.0, 0.0, 1.0 ]
```
The function has the following parameters:
- **a**: rotational elimination parameter.
- **b**: rotational elimination parameter.
#### drotg.assign( a, b, out, stride, offset )
Constructs a Givens plane rotation provided two double-precision floating-point values `a` and `b` and assigns results to an output array.
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var out = new Float64Array( 4 );
var y = drotg.assign( 0.0, 2.0, out, 1, 0 );
// returns [ 2.0, 1.0, 0.0, 1.0 ]
var bool = ( y === out );
// returns true
```
## Notes
- `drotg()` corresponds to the [BLAS][blas] level 1 function [`drotg`][blas-drotg].
```javascript
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var drotg = require( '@stdlib/blas/base/drotg' );
var out;
var i;
for ( i = 0; i < 100; i++ ) {
out = drotg( discreteUniform( -5, 5 ), discreteUniform( -5, 5 ) );
console.log( out );
}
```
[blas]: http://www.netlib.org/blas
[blas-drotg]: https://www.netlib.org/lapack/explore-html/d7/dc5/group__rotg_gaafa91c51f75df6c3f2182032a221c2db.html#gaafa91c51f75df6c3f2182032a221c2db