crot

Apply a plane rotation with real cosine and complex sine to a pair of single-precision complex floating-point vectors.

Installation

npm install @stdlib/lapack-base-crot

Usage

var crot = require( '@stdlib/lapack-base-crot' );

crot( N, cx, strideCX, cy, strideCY, c, s )

Applies a plane rotation with real cosine and complex sine.

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var cy = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var s = new Complex64( 0.0, 0.75 );

crot( cx.length, cx, 1, cy, 1, 1.25, s );

var z = cy.get( 0 );
// returns <Complex64>[ ~-1.5, ~0.75 ]

z = cx.get( 0 );
// returns <Complex64>[ ~1.25, ~2.5 ]

The function has the following parameters:

• N: number of indexed elements.
• cx: first input Complex64Array.
• strideCX: stride length for cx.
• cy: second input Complex64Array.
• strideCY: stride length for cy.

The N and stride parameters determine how values from cx and cy are accessed at runtime. For example, to apply a plane rotation to every other element,

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var cy = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var s = new Complex64( 0.0, 0.75 );

crot( 2, cx, 2, cy, 2, 1.25, s );

var z = cy.get( 0 );
// returns <Complex64>[ ~-1.5, ~0.75 ]

z = cx.get( 0 );
// returns <Complex64>[ ~1.25, ~2.5 ]

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

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

// Initial arrays...
var cx0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var cy0 = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var cx1 = new Complex64Array( cx0.buffer, cx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var cy1 = new Complex64Array( cy0.buffer, cy0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

var s = new Complex64( 0.0, 0.75 );

crot( 2, cx1, -2, cy1, 1, 1.25, s );

var z = cy0.get( 2 );
// returns <Complex64>[ ~-6.0, ~5.25 ]

z = cx0.get( 3 );
// returns <Complex64>[ ~8.75, ~10.0 ]

crot.ndarray( N, cx, strideCX, offsetCX, cy, strideCY, offsetCY, c, s )

Applies a plane rotation with real cosine and complex sine using alternative indexing semantics.

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var cy = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var s = new Complex64( 0.0, 0.75 );

crot.ndarray( cx.length, cx, 1, 0, cy, 1, 0, 1.25, s );

var z = cy.get( 0 );
// returns <Complex64>[ ~-1.5, ~0.75 ]

z = cx.get( 0 );
// returns <Complex64>[ ~1.25, ~2.5 ]

The function has the following additional parameters:

• offsetCX: starting index for cx.
• offsetCY: starting index for cy.

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, to apply a plane rotation to every other element starting from the second element,

var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );

var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var cy = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var s = new Complex64( 0.0, 0.75 );

crot.ndarray( 2, cx, 2, 1, cy, 2, 1, 1.25, s );

var z = cy.get( 3 );
// returns <Complex64>[ ~-6.0, ~5.25 ]

z = cx.get( 1 );
// returns <Complex64>[ ~3.75, ~5.0 ]

Notes

• If N <= 0, both functions leave cx and cy unchanged.
• crot() corresponds to the LAPACK routine crot.

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );
var ccopy = require( '@stdlib/blas-base-ccopy' );
var zeros = require( '@stdlib/array-zeros' );
var logEach = require( '@stdlib/console-log-each' );
var crot = require( '@stdlib/lapack-base-crot' );

function rand() {
    return new Complex64( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
}

// Generate random input arrays:
var cx = filledarrayBy( 10, 'complex64', rand );
var cxc = ccopy( cx.length, cx, 1, zeros( cx.length, 'complex64' ), 1 );

var cy = filledarrayBy( 10, 'complex64', rand );
var cyc = ccopy( cy.length, cy, 1, zeros( cy.length, 'complex64' ), 1 );

var s = new Complex64( 0.0, 0.75 );

// Apply a plane rotation:
crot( cx.length, cx, 1, cy, 1, 1.25, s );

// Print the results:
logEach( '(%s,%s) => (%s,%s)', cxc, cyc, cx, cy );

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.