https://github.com/stdlib-js/strided-base-dmskmap

Apply a unary function accepting and returning double-precision floating-point numbers to each element in a double-precision floating-point strided input array according to a corresponding element in a strided mask array and assign each result to an element in a double-precision floating-point strided output array.
https://github.com/stdlib-js/strided-base-dmskmap

apply array base dbl double double-precision float64 foreach javascript map mask masked ndarray node node-js nodejs stdlib strided transform unary

Last synced: about 2 months ago
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Apply a unary function accepting and returning double-precision floating-point numbers to each element in a double-precision floating-point strided input array according to a corresponding element in a strided mask array and assign each result to an element in a double-precision floating-point strided output array.

• Host: GitHub
• URL: https://github.com/stdlib-js/strided-base-dmskmap
• Owner: stdlib-js
• License: apache-2.0
• Created: 2021-06-14T13:18:00.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2024-11-01T03:28:08.000Z (2 months ago)
• Last Synced: 2024-11-11T05:57:33.873Z (about 2 months ago)
• Topics: apply, array, base, dbl, double, double-precision, float64, foreach, javascript, map, mask, masked, ndarray, node, node-js, nodejs, stdlib, strided, transform, unary
• Language: JavaScript
• Homepage: https://github.com/stdlib-js/stdlib
• Size: 488 KB
• Stars: 1
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE
  • Code of conduct: CODE_OF_CONDUCT.md
  • Citation: CITATION.cff
  • Security: SECURITY.md

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# dmskmap

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

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

## Installation

```bash

npm install @stdlib/strided-base-dmskmap

```

Alternatively,

-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).

The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

## Usage

```javascript

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

```

#### dmskmap( N, x, strideX, mask, strideMask, y, strideY, fcn )

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

```javascript

var Float64Array = require( '@stdlib/array-float64' );

var Uint8Array = require( '@stdlib/array-uint8' );

var abs = require( '@stdlib/math-base-special-abs' );

var x = new Float64Array( [ -2.0, 1.0, -3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

var m = new Uint8Array( [ 0, 0, 1, 0, 0, 1, 1, 0 ] );

// Compute the absolute values in-place:

dmskmap( x.length, x, 1, m, 1, x, 1, abs );

// x => [ 2.0, 1.0, -3.0, 5.0, 4.0, 0.0, -1.0, 3.0 ]

```

The function accepts the following arguments:

-   **N**: number of indexed elements.

-   **x**: input [`Float64Array`][@stdlib/array/float64].

-   **strideX**: index increment for `x`.

-   **mask**: mask [`Uint8Array`][@stdlib/array/uint8].

-   **strideMask**: index increment for `mask`.

-   **y**: output [`Float64Array`][@stdlib/array/float64].

-   **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 Float64Array = require( '@stdlib/array-float64' );

var Uint8Array = require( '@stdlib/array-uint8' );

var abs = require( '@stdlib/math-base-special-abs' );

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );

var m = new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] );

var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmskmap( 3, x, 2, m, 2, y, -1, abs );

// y => [ 5.0, 0.0, 1.0, 0.0, 0.0, 0.0 ]

```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][@stdlib/array/float64] views.

```javascript

var Float64Array = require( '@stdlib/array-float64' );

var Uint8Array = require( '@stdlib/array-uint8' );

var abs = require( '@stdlib/math-base-special-abs' );

// Initial arrays...

var x0 = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );

var m0 = new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] );

var y0 = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...

var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var m1 = new Uint8Array( m0.buffer, m0.BYTES_PER_ELEMENT*3 ); // start at 4th element

var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element

dmskmap( 3, x1, -2, m1, 1, y1, 1, abs );

// y0 => [ 0.0, 0.0, 0.0, 6.0, 4.0, 0.0 ]

```

#### dmskmap.ndarray( N, x, strideX, offsetX, mask, strideMask, offsetMask, y, strideY, offsetY, fcn )

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

```javascript

var Float64Array = require( '@stdlib/array-float64' );

var Uint8Array = require( '@stdlib/array-uint8' );

var abs = require( '@stdlib/math-base-special-abs' );

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );

var m = new Uint8Array( [ 0, 0, 1, 0, 0 ] );

var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmskmap.ndarray( x.length, x, 1, 0, m, 1, 0, y, 1, 0, abs );

// y => [ 1.0, 2.0, 0.0, 4.0, 5.0 ]

```

The function accepts the following additional arguments:

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

-   **offsetMask**: starting index for `mask`.

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

While [`typed array`][@stdlib/array/float64] views mandate a view offset based on the underlying `buffer`, the `offsetX` and `offsetY` 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 Float64Array = require( '@stdlib/array-float64' );

var Uint8Array = require( '@stdlib/array-uint8' );

var abs = require( '@stdlib/math-base-special-abs' );

var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );

var m = new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] );

var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dmskmap.ndarray( 3, x, 2, 1, m, 2, 1, y, -1, y.length-1, abs );

// y => [ 0.0, 0.0, 0.0, 0.0, 4.0, 2.0 ]

```

## Examples

```javascript

var round = require( '@stdlib/math-base-special-round' );

var randu = require( '@stdlib/random-base-randu' );

var bernoulli = require( '@stdlib/random-base-bernoulli' );

var Float64Array = require( '@stdlib/array-float64' );

var Uint8Array = require( '@stdlib/array-uint8' );

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

function scale( x ) {

    return x * 10.0;

}

var x = new Float64Array( 10 );

var m = new Uint8Array( x.length );

var y = new Float64Array( x.length );

var i;

for ( i = 0; i < x.length; i++ ) {

    x[ i ] = round( (randu()*200.0) - 100.0 );

    m[ i ] = bernoulli( 0.2 );

}

console.log( x );

console.log( m );

console.log( y );

dmskmap.ndarray( x.length, x, 1, 0, m, 1, 0, y, -1, y.length-1, scale );

console.log( y );

```

* * *

## C APIs

### Usage

```c

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

```

#### stdlib_strided_dmskmap( N, \*X, strideX, \*Mask, strideMask, \*Y, strideY, fcn )

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

```c

#include 

static double scale( const double x ) {

    return x * 10.0;

}

double X[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };

uint8_t M[] = { 0, 0, 1, 0, 0, 1 };

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

int64_t N = 6;

stdlib_strided_dmskmap( N, X, 1, M, 1, Y, 1, scale );

```

The function accepts the following arguments:

-   **N**: `[in] int64_t` number of indexed elements.

-   **X**: `[in] double*` input array.

-   **strideX** `[in] int64_t` index increment for `X`.

-   **Mask**: `[in] uint8_t*` mask array.

-   **strideMask**: `[in] int64_t` index increment for `Mask`.

-   **Y**: `[out] double*` output array.

-   **strideY**: `[in] int64_t` index increment for `Y`.

-   **fcn**: `[in] double (*fcn)( double )` unary function to apply.

```c

void stdlib_strided_dmskmap( const int64_t N, const double *X, const int64_t strideX, const uint8_t *Mask, const int64_t strideMask, double *Y, const int64_t strideY, double (*fcn)( double ) );

```

### Examples

```c

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

#include 

#include 

#include 

// Define a callback:

static double scale( const double x ) {

    return x * 10.0;

}

int main( void ) {

    // Create an input strided array:

    double X[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };

    // Create a mask strided array:

    uint8_t M[] = { 0, 0, 1, 0, 0, 1 };

    // Create an output strided array:

    double 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 strideM = 1;

    int64_t strideY = -1;

    // Apply the callback:

    stdlib_strided_dmskmap( N, X, strideX, M, strideM, Y, strideY, scale );

    // Print the results:

    for ( int64_t i = 0; i < N; i++ ) {

        printf( "Y[ %"PRId64" ] = %lf\n", i, Y[ i ] );

    }

}

```

* * *

## See Also

-   [`@stdlib/strided-base/dmap`][@stdlib/strided/base/dmap]: 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.

-   [`@stdlib/strided-base/dmskmap2`][@stdlib/strided/base/dmskmap2]: apply a binary function to double-precision floating-point strided input arrays according to a strided mask array and assign results to a double-precision floating-point strided output array.

-   [`@stdlib/strided-base/mskunary`][@stdlib/strided/base/mskunary]: apply a unary callback to elements in a strided input array according to elements in a strided mask array and assign results to elements in a strided output array.

-   [`@stdlib/strided-base/smskmap`][@stdlib/strided/base/smskmap]: apply a unary function to a single-precision floating-point strided input array according to a strided mask array and assign results to a single-precision floating-point strided output array.

* * *

## 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 © 2016-2024. The Stdlib [Authors][stdlib-authors].

[npm-image]: http://img.shields.io/npm/v/@stdlib/strided-base-dmskmap.svg

[npm-url]: https://npmjs.org/package/@stdlib/strided-base-dmskmap

[test-image]: https://github.com/stdlib-js/strided-base-dmskmap/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/strided-base-dmskmap/actions/workflows/test.yml?query=branch:main

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/strided-base-dmskmap/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/strided-base-dmskmap?branch=main

[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im

[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

[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-dmskmap/tree/deno

[deno-readme]: https://github.com/stdlib-js/strided-base-dmskmap/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/strided-base-dmskmap/tree/umd

[umd-readme]: https://github.com/stdlib-js/strided-base-dmskmap/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/strided-base-dmskmap/tree/esm

[esm-readme]: https://github.com/stdlib-js/strided-base-dmskmap/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/strided-base-dmskmap/blob/main/branches.md

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

[@stdlib/array/float64]: https://github.com/stdlib-js/array-float64

[@stdlib/array/uint8]: https://github.com/stdlib-js/array-uint8

[@stdlib/strided/base/dmap]: https://github.com/stdlib-js/strided-base-dmap

[@stdlib/strided/base/dmskmap2]: https://github.com/stdlib-js/strided-base-dmskmap2

[@stdlib/strided/base/mskunary]: https://github.com/stdlib-js/strided-base-mskunary

[@stdlib/strided/base/smskmap]: https://github.com/stdlib-js/strided-base-smskmap