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drot

Applies a plane rotation.

Usage

var drot = require( '@stdlib/blas/base/drot' );

drot( N, x, strideX, y, strideY, c, s )

Applies a plane rotation.

var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );

drot( x.length, x, 1, y, 1, 1.0, 0.0 );
// x => <Float64Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]
// y => <Float64Array>[ 6.0, 7.0, 8.0, 9.0, 10.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • x: first input Float64Array.
  • strideX: index increment for x.
  • y: second input Float64Array.
  • strideY: index increment for y.
  • c: double precision cosine.
  • s: double precision sin.

The N and stride parameters determine how values in the strided arrays are accessed at runtime. For example, to apply plane rotation for the strided arrays in reverse order.

var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );

drot( x.length, x, 2, y, 2, 0.707, 0.707 );
// x => <Float64Array>[ 5.656, 2.0, 8.484, 4.0, 11.312, 6.0 ]
// y => <Float64Array>[ 4.242, 8.0, 4.241999999999999, 10.0, 4.241999999999999, 12.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

drot.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, c, s )

Applies a plane rotation.

var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );

drot.ndarray( x.length, x, 1, 0, y, 1, 0, 1.0, 0.0 );
// x => <Float64Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]
// y => <Float64Array>[ 6.0, 7.0, 8.0, 9.0, 10.0 ]

The function has the following additional parameters:

  • offsetX: starting index for x.
  • offsetY: starting index for y.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, for offset of two in x rotate every other value in x starting from the second value,...,

var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );

drot.ndarray( 4, x, 0, 2, y, 0, 2, 0.707, 0.707 );
// x => <Float64Array>[ 1.0, 2.0, -2.998188273612, 4.0, 5.0, 6.0 ]
// y => <Float64Array>[ 7.0, 8.0, -8.994564820835999, 10.0, 11.0, 12.0 ]

Notes

  • If N <= 0, both functions leave x and y unchanged.
  • drot() corresponds to the BLAS level 1 function drot.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var drot = require( '@stdlib/blas/base/drot' );

var opts = {
    'dtype': 'float64'
};
var x = discreteUniform( 10, 0, 500, opts );
console.log( x );

var y = discreteUniform( x.length, 0, 255, opts );
console.log( y );

// Applies a plane rotation :
drot( x.length, x, 1, y, 1, 0.707, 0.707 );
console.log( x );
console.log( y );

See Also