stdlib-js
<summary>
About stdlib...
</summary>
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gcopy
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
Copy values from
xintoy.
bash
npm install @stdlib/blas-base-gcopy
javascript
var gcopy = require( '@stdlib/blas-base-gcopy' );
#### gcopy( N, x, strideX, y, strideY )
Copies values from x into y.
javascript
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];
var y = [ 6.0, 7.0, 8.0, 9.0, 10.0 ];
gcopy( x.length, x, 1, y, 1 );
// y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ]
The function has the following parameters:
- N: number of indexed elements.
- x: input array.
- strideX: index increment for x.
- y: output array.
- strideY: index increment for y.
The N and stride parameters determine how values from x are copied into y. For example, to copy in reverse order every other value in x into the first N elements of y,
javascript
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var y = [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ];
gcopy( 3, x, -2, y, 1 );
// y => [ 5.0, 3.0, 1.0, 10.0, 11.0, 12.0 ]
Note that indexing is relative to the first index. To introduce an offset, use [typed array][mdn-typed-array] views.
javascript
var Float64Array = require( '@stdlib/array-float64' );
// 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
// Copy in reverse order every other value from `x1` into `y1`...
gcopy( 3, x1, -2, y1, 1 );
// y0 => <Float64Array>[ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]
#### gcopy.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )
Copies values from x into y using alternative indexing semantics.
javascript
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];
var y = [ 6.0, 7.0, 8.0, 9.0, 10.0 ];
gcopy.ndarray( x.length, x, 1, 0, y, 1, 0 );
// y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ]
The function has the following additional parameters:
- offsetX: starting index for x.
- offsetY: starting index for y.
While [typed array][mdn-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 copy every other value in x starting from the second value into the last N elements in y where x[i] = y[n], x[i+2] = y[n-1],...,
javascript
var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var y = [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ];
gcopy.ndarray( 3, x, 2, 1, y, -1, y.length-1 );
// y => [ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]
N <= 0, both functions return y unchanged.
- Both functions support array-like objects having getter and setter accessors for array element access (e.g., [@stdlib/array-complex64][@stdlib/array/complex64]).
- gcopy() corresponds to the [BLAS][blas] level 1 function [dcopy][dcopy] with the exception that this implementation works with any array type, not just Float64Arrays. Depending on the environment, the typed versions ([dcopy][@stdlib/blas/base/dcopy], [scopy][@stdlib/blas/base/scopy], etc.) are likely to be significantly more performant.
javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var gcopy = require( '@stdlib/blas-base-gcopy' );
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 );
// Copy elements from `x` into `y` starting from the end of `y`:
gcopy( x.length, x, 1, y, -1 );
console.log( y );
@stdlib/blas-base/dcopy][@stdlib/blas/base/dcopy]: copy values from x into y.
- [@stdlib/blas-base/scopy][@stdlib/blas/base/scopy]: copy values from x into y.
