@stdlib/strided-base-cmap

About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

cmap

Apply a unary function to a single-precision floating-point strided input array and assign results to a single-precision floating-point strided output array.

Installation

npm install @stdlib/strided-base-cmap

Usage

var cmap = require( '@stdlib/strided-base-cmap' );

cmap( N, x, strideX, y, strideY, fcn )

Applies a unary function to a single-precision complex floating-point strided input array and assigns results to a single-precision complex floating-point strided output array.

var Complex64Array = require( '@stdlib/array-complex64' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var cceilf = require( '@stdlib/math-base-special-cceilf' );

var x = new Complex64Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex64Array( x.length );

cmap( x.length, x, 1, y, 1, cceilf );

var v = y.get( 0 );
// returns <Complex64>

var re = real( v );
// returns -2.0

var im = imag( v );
// returns 2.0

The function accepts the following arguments:

• N: number of indexed elements.
• x: input Complex64Array.
• strideX: index increment for x.
• y: output Complex64Array.
• strideY: index increment for y.
• fcn: function to apply.

The N and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to index every other value in x and to index the first N elements of y in reverse order,

var Complex64Array = require( '@stdlib/array-complex64' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var cceilf = require( '@stdlib/math-base-special-cceilf' );

var x = new Complex64Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex64Array( x.length );

cmap( 2, x, 2, y, -1, cceilf );

var v = y.get( 0 );
// returns <Complex64>

var re = real( v );
// returns 5.0

var im = imag( v );
// returns 0.0

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

var Complex64Array = require( '@stdlib/array-complex64' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var cceilf = require( '@stdlib/math-base-special-cceilf' );

// Initial arrays...
var x0 = new Complex64Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y0 = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Complex64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Complex64Array( y0.buffer, y0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

cmap( 2, x1, -2, y1, 1, cceilf );

var v = y0.get( 2 );
// returns <Complex64>

var re = real( v );
// returns -1.0

var im = imag( v );
// returns 4.0

cmap.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, fcn )

Applies a unary function to a single-precision complex floating-point strided input array and assigns results to a single-precision complex floating-point strided output array using alternative indexing semantics.

var Complex64Array = require( '@stdlib/array-complex64' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var cceilf = require( '@stdlib/math-base-special-cceilf' );

var x = new Complex64Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex64Array( x.length );

cmap.ndarray( x.length, x, 1, 0, y, 1, 0, cceilf );

var v = y.get( 0 );
// returns <Complex64>

var re = real( v );
// returns -2.0

var im = imag( v );
// returns 2.0

The function accepts the following additional arguments:

• 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 index every other value in x starting from the second value and to index the last N elements in y in reverse order,

var Complex64Array = require( '@stdlib/array-complex64' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var cceilf = require( '@stdlib/math-base-special-cceilf' );

var x = new Complex64Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex64Array( x.length );

cmap.ndarray( 2, x, 2, 1, y, -1, y.length-1, cceilf );

var v = y.get( y.length-1 );
// returns <Complex64>

var re = real( v );
// returns 4.0

var im = imag( v );
// returns -5.0

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory;
var Complex64Array = require( '@stdlib/array-complex64' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var real = require( '@stdlib/complex-real' );
var imag = require( '@stdlib/complex-imag' );
var Complex64 = require( '@stdlib/complex-float32' );
var cmap = require( '@stdlib/strided-base-cmap' );

function scale( x ) {
    var re = real( x );
    var im = imag( x );
    return new Complex64( re*10.0, im*10.0 );
}

var xbuf = filledarrayBy( 10*2, 'float32', discreteUniform( -100.0, 100.0 ) );
var x = new Complex64Array( xbuf.buffer );
console.log( x );

var y = new Complex64Array( x.length );
console.log( y );

cmap.ndarray( x.length, x, 1, 0, y, -1, y.length-1, scale );
console.log( y );

---

C APIs

Usage

#include "stdlib/strided/base/cmap.h"

stdlib_strided_cmap( N, *X, strideX, *Y, strideY, fcn )

Applies a unary function to a single-precision complex floating-point strided input array and assigns results to a single-precision complex floating-point strided output array.

#include <stdint.h>
#include <complex.h>

static float complex scale( const float complex x ) {
    float re = crealf( x );
    float im = cimagf( x );
    return ( re+10.0f ) + ( im+10.0f )*I;
}

float complex X[] = { 1.0f+1.0f*I, 2.0f+2.0f*I, 3.0f+3.0f*I, 4.0f+4.0f*I, 5.0f+5.0f*I, 6.0f+6.0f*I };
float complex Y[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };

int64_t N = 6;

stdlib_strided_cmap( N, X, 1, Y, 1, scale );

The function accepts the following arguments:

• N: [in] int64_t number of indexed elements.
• X: [in] float complex* input array.
• strideX [in] int64_t index increment for X.
• Y: [out] float complex* output array.
• strideY: [in] int64_t index increment for Y.
• fcn: [in] float complex (*fcn)( float complex ) unary function to apply.

void stdlib_strided_cmap( const int64_t N, const float complex *X, const int64_t strideX, float complex *Y, const int64_t strideY, float complex (*fcn)( float complex ) );

Examples

#include "stdlib/strided/base/cmap.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
#include <complex.h>

// Define a callback:
static float complex scale( const float complex x ) {
    float re = crealf( x );
    float im = cimagf( x );
    return ( re+10.0f ) + ( im+10.0f )*I;
}

int main( void ) {
    // Create an input strided array:
    float complex X[] = { 1.0+1.0*I, 2.0+2.0*I, 3.0+3.0*I, 4.0+4.0*I, 5.0+5.0*I, 6.0+6.0*I };

    // Create an output strided array:
    float complex Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };

    // Specify the number of elements:
    int64_t N = 6;

    // Define the strides:
    int64_t strideX = 1;
    int64_t strideY = -1;

    // Apply the callback:
    stdlib_strided_cmap( N, X, strideX, Y, strideY, scale );

    // Print the results:
    for ( int64_t i = 0; i < N; i++ ) {
        printf( "Y[ %"PRId64" ] = %f + %fi\n", i, creal( Y[i] ), cimag( Y[i] ) );
    }
}

---

See Also

• @stdlib/strided-base/zmap: apply a unary function to a double-precision complex floating-point strided input array and assign results to a double-precision complex floating-point strided output array.
• @stdlib/strided-base/unary: apply a unary callback to elements in a strided input array and assign results to elements in a strided output array.

---

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 © 2016-2024. The Stdlib Authors.