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https://github.com/stdlib-js/stats-base-dmediansorted
Calculate the median value of a sorted double-precision floating-point strided array.
https://github.com/stdlib-js/stats-base-dmediansorted
average avg central-tendency javascript math mathematics median middle node node-js nodejs ordered quantile sorted statistics stats stdlib strided strided-array typed
Last synced: about 18 hours ago
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Calculate the median value of a sorted double-precision floating-point strided array.
- Host: GitHub
- URL: https://github.com/stdlib-js/stats-base-dmediansorted
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T13:28:21.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2024-11-01T06:53:31.000Z (17 days ago)
- Last Synced: 2024-11-11T18:34:20.165Z (6 days ago)
- Topics: average, avg, central-tendency, javascript, math, mathematics, median, middle, node, node-js, nodejs, ordered, quantile, sorted, statistics, stats, stdlib, strided, strided-array, typed
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 493 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
Awesome Lists containing this project
README
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# dmediansorted
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Calculate the median value of a sorted double-precision floating-point strided array.
## Installation
```bash
npm install @stdlib/stats-base-dmediansorted
```
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 dmediansorted = require( '@stdlib/stats-base-dmediansorted' );
```
#### dmediansorted( N, x, stride )
Computes the median value of a sorted double-precision floating-point strided array `x`.
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0 ] );
var v = dmediansorted( x.length, x, 1 );
// returns 2.0
x = new Float64Array( [ 3.0, 2.0, 1.0 ] );
v = dmediansorted( x.length, x, 1 );
// returns 2.0
```
The function has the following parameters:
- **N**: number of indexed elements.
- **x**: sorted input [`Float64Array`][@stdlib/array/float64].
- **stride**: index increment for `x`.
The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to compute the median value of every other element in `x`,
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var floor = require( '@stdlib/math-base-special-floor' );
var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, 3.0, 3.0, 4.0, 2.0 ] );
var N = floor( x.length / 2 );
var v = dmediansorted( N, x, 2 );
// returns 2.5
```
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' );
var floor = require( '@stdlib/math-base-special-floor' );
var x0 = new Float64Array( [ 2.0, 1.0, 2.0, 2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var N = floor( x0.length / 2 );
var v = dmediansorted( N, x1, 2 );
// returns 2.0
```
#### dmediansorted.ndarray( N, x, stride, offset )
Computes the median value of a sorted double-precision floating-point strided array using alternative indexing semantics.
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0 ] );
var N = x.length;
var v = dmediansorted.ndarray( N, x, 1, 0 );
// returns 2.0
```
The function has the following additional parameters:
- **offset**: starting index for `x`.
While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the median value for every other value in `x` starting from the second value
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var floor = require( '@stdlib/math-base-special-floor' );
var x = new Float64Array( [ 2.0, 1.0, 2.0, 2.0, -2.0, 2.0, 3.0, 4.0 ] );
var N = floor( x.length / 2 );
var v = dmediansorted.ndarray( N, x, 2, 1 );
// returns 2.0
```
## Notes
- If `N <= 0`, both functions return `NaN`.
- The input strided array must be sorted in either **strictly** ascending or descending order.
## Examples
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var dmediansorted = require( '@stdlib/stats-base-dmediansorted' );
var x;
var i;
x = new Float64Array( 10 );
for ( i = 0; i < x.length; i++ ) {
x[ i ] = i - 5.0;
}
console.log( x );
var v = dmediansorted( x.length, x, 1 );
console.log( v );
```
* * *
## See Also
- [`@stdlib/stats-base/dmean`][@stdlib/stats/base/dmean]: calculate the arithmetic mean of a double-precision floating-point strided array.
- [`@stdlib/stats-base/mediansorted`][@stdlib/stats/base/mediansorted]: calculate the median value of a sorted strided array.
- [`@stdlib/stats-base/smediansorted`][@stdlib/stats/base/smediansorted]: calculate the median value of a sorted single-precision floating-point strided 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/stats-base-dmediansorted.svg
[npm-url]: https://npmjs.org/package/@stdlib/stats-base-dmediansorted
[test-image]: https://github.com/stdlib-js/stats-base-dmediansorted/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/stats-base-dmediansorted/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/stats-base-dmediansorted/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/stats-base-dmediansorted?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/stats-base-dmediansorted/tree/deno
[deno-readme]: https://github.com/stdlib-js/stats-base-dmediansorted/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/stats-base-dmediansorted/tree/umd
[umd-readme]: https://github.com/stdlib-js/stats-base-dmediansorted/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/stats-base-dmediansorted/tree/esm
[esm-readme]: https://github.com/stdlib-js/stats-base-dmediansorted/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/stats-base-dmediansorted/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/stats-base-dmediansorted/main/LICENSE
[@stdlib/array/float64]: https://github.com/stdlib-js/array-float64
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[@stdlib/stats/base/dmean]: https://github.com/stdlib-js/stats-base-dmean
[@stdlib/stats/base/mediansorted]: https://github.com/stdlib-js/stats-base-mediansorted
[@stdlib/stats/base/smediansorted]: https://github.com/stdlib-js/stats-base-smediansorted