npm package: @stdlib/strided-base-zmap
Description: 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.
Author: The Stdlib Authors
Latest version: 0.2.3

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# zmap

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

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

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/strided-base-zmap
```

</section>

<section class="usage">

## Usage

```javascript
var zmap = require( '@stdlib/strided-base-zmap' );
```

#### zmap( N, x, strideX, y, strideY, fcn )

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

```javascript
var Complex128Array = require( '@stdlib/array-complex128' );
var cceil = require( '@stdlib/math-base-special-cceil' );

var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );

zmap( x.length, x, 1, y, 1, cceil );

var v = y.get( 0 );
// returns <Complex128>[ -2.0, 2.0 ]
```

The function accepts the following arguments:

-   **N**: number of indexed elements.
-   **x**: input [`Complex128Array`][@stdlib/array/complex128].
-   **strideX**: index increment for `x`.
-   **y**: output [`Complex128Array`][@stdlib/array/complex128].
-   **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,

```javascript
var Complex128Array = require( '@stdlib/array-complex128' );
var cceil = require( '@stdlib/math-base-special-cceil' );

var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );

zmap( 2, x, 2, y, -1, cceil );

var v = y.get( 0 );
// returns <Complex128>[ 5.0, 0.0 ]
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][@stdlib/array/complex128] views.

```javascript
var Complex128Array = require( '@stdlib/array-complex128' );
var cceil = require( '@stdlib/math-base-special-cceil' );

// Initial arrays...
var x0 = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y0 = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Complex128Array( y0.buffer, y0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

zmap( 2, x1, -2, y1, 1, cceil );

var v = y0.get( 2 );
// returns <Complex128>[ -1.0, 4.0 ]
```

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

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

```javascript
var Complex128Array = require( '@stdlib/array-complex128' );
var cceil = require( '@stdlib/math-base-special-cceil' );

var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );

zmap.ndarray( x.length, x, 1, 0, y, 1, 0, cceil );

var v = y.get( 0 );
// returns <Complex128>[ -2.0, 2.0 ]
```

The function accepts the following additional arguments:

-   **offsetX**: starting index for `x`.
-   **offsetY**: starting index for `y`.

While [`typed array`][@stdlib/array/complex128] 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,

```javascript
var Complex128Array = require( '@stdlib/array-complex128' );
var cceil = require( '@stdlib/math-base-special-cceil' );

var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );

zmap.ndarray( 2, x, 2, 1, y, -1, y.length-1, cceil );

var v = y.get( y.length-1 );
// returns <Complex128>[ 4.0, -5.0 ]
```

</section>

<!-- /.usage -->

<section class="notes">

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory;
var Complex128Array = require( '@stdlib/array-complex128' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var real = require( '@stdlib/complex-float64-real' );
var imag = require( '@stdlib/complex-float64-imag' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );
var zmap = require( '@stdlib/strided-base-zmap' );

function scale( x ) {
    var re = real( x );
    var im = imag( x );
    return new Complex128( re*10.0, im*10.0 );
}

var xbuf = filledarrayBy( 10*2, 'float64', discreteUniform( -100.0, 100.0 ) );
var x = new Complex128Array( xbuf.buffer );
console.log( x );

var y = new Complex128Array( x.length );
console.log( y );

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

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/strided/base/zmap.h"
```

#### stdlib_strided_zmap( N, \*X, strideX, \*Y, strideY, fcn )

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

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

static double complex scale( const double complex x ) {
    double re = creal( x );
    double im = cimag( x );
    return ( re+10.0 ) + ( im+10.0 )*I;
}

double 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 };
double complex Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };

int64_t N = 6;

stdlib_strided_zmap( N, X, 1, Y, 1, scale );
```

The function accepts the following arguments:

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

```c
void stdlib_strided_zmap( const int64_t N, const double complex *X, const int64_t strideX, double complex *Y, const int64_t strideY, double complex (*fcn)( double complex ) );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/strided/base/zmap.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
#include <complex.h>

// Define a callback:
static double complex scale( const double complex x ) {
    double re = creal( x );
    double im = cimag( x );
    return ( re+10.0 ) + ( im+10.0 )*I;
}

int main( void ) {
    // Create an input strided array:
    double 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:
    double 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_zmap( N, X, strideX, Y, strideY, scale );

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

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/strided-base/cmap`][@stdlib/strided/base/cmap]</span><span class="delimiter">: </span><span class="description">apply a unary function to a single-precision complex floating-point strided input array and assign results to a single-precision complex floating-point strided output array.</span>
-   <span class="package-name">[`@stdlib/strided-base/unary`][@stdlib/strided/base/unary]</span><span class="delimiter">: </span><span class="description">apply a unary callback to elements in a strided input array and assign results to elements in a strided output array.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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<section class="links">

[npm-image]: http://img.shields.io/npm/v/@stdlib/strided-base-zmap.svg
[npm-url]: https://npmjs.org/package/@stdlib/strided-base-zmap

[test-image]: https://github.com/stdlib-js/strided-base-zmap/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/strided-base-zmap/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/strided-base-zmap/main.svg
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/strided-base-zmap/tree/deno
[deno-readme]: https://github.com/stdlib-js/strided-base-zmap/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/strided-base-zmap/tree/umd
[umd-readme]: https://github.com/stdlib-js/strided-base-zmap/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/strided-base-zmap/tree/esm
[esm-readme]: https://github.com/stdlib-js/strided-base-zmap/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/strided-base-zmap/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/strided-base-zmap/main/LICENSE

[@stdlib/array/complex128]: https://www.npmjs.com/package/@stdlib/array-complex128

<!-- <related-links> -->

[@stdlib/strided/base/cmap]: https://www.npmjs.com/package/@stdlib/strided-base-cmap

[@stdlib/strided/base/unary]: https://www.npmjs.com/package/@stdlib/strided-base-unary

<!-- </related-links> -->

</section>

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