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Apply a plane rotation.
This BLAS level 1 routine applies a real plane rotation to real double-precision floating-point vectors. The plane rotation is applied to N points, where the points to be rotated are contained in vectors x and y and where the cosine and sine of the angle of rotation are c and s, respectively. The operation is as follows:
where x_i and y_i are the individual elements on which the rotation is applied.
import drot from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-base-drot@esm/index.mjs';Applies a plane rotation.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
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, 0.8, 0.6 );
// x => <Float64Array>[ ~4.4, ~5.8, 7.2, 8.6, 10.0 ]
// y => <Float64Array>[ ~4.2, 4.4, 4.6, 4.8, 5.0 ]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: cosine of the angle of rotation.
- s: sine of the angle of rotation.
The N and stride parameters determine how values in the strided arrays are accessed at runtime. For example, to apply a plane rotation to every other element,
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
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( 3, x, 2, y, 2, 0.8, 0.6 );
// x => <Float64Array>[ 5.0, 2.0, 7.8, 4.0, 10.6, 6.0 ]
// y => <Float64Array>[ ~5.0, 8.0, 5.4, 10.0, ~5.8, 12.0 ]Note that indexing is relative to the first index. To introduce an offset, use typed array views.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
drot( 3, x1, -2, y1, 1, 0.8, 0.6 );
// x0 => <Float64Array>[ 1.0, ~8.8, 3.0, 9.8, 5.0, 10.8 ]
// y0 => <Float64Array>[ 7.0, 8.0, 9.0, 4.4, 6.4, ~8.4 ]Applies a plane rotation using alternative indexing semantics.
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
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( 4, x, 1, 1, y, 1, 1, 0.8, 0.6 );
// x => <Float64Array>[ 1.0, ~5.8, 7.2, 8.6, 10.0 ]
// y => <Float64Array>[ 6.0, 4.4, ~4.6, ~4.8, 5.0 ]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, to apply a plane rotation to every other element starting from the second element,
import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@esm/index.mjs';
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( 3, x, 2, 1, y, 2, 1, 0.8, 0.6 );
// x => <Float64Array>[ 1.0, 6.4, 3.0, 9.2, 5.0, 12.0 ]
// y => <Float64Array>[ 7.0, 5.2, 9.0, 5.6, 11.0, ~6.0 ]<!DOCTYPE html>
<html lang="en">
<body>
<script type="module">
import discreteUniform from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@esm/index.mjs';
import drot from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-base-drot@esm/index.mjs';
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 );
// Apply a plane rotation:
drot( x.length, x, 1, y, 1, 0.8, 0.6 );
console.log( x );
console.log( y );
</script>
</body>
</html>This package is part of stdlib, a standard library 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.
See LICENSE.
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