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# incrhmean [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] > Compute a [harmonic mean][harmonic-mean] incrementally.
The [harmonic mean][harmonic-mean] of positive real numbers `x_0, x_1, ..., x_{n-1}` is defined as ```math \begin{align}H &= \frac{n}{\frac{1}{x_0} + \frac{1}{x_1} + \cdots + \frac{1}{x_{n-1}}} \\ &= \frac{\displaystyle n}{\displaystyle\sum_{i=0}^{n-1} \frac{1}{x_i}} \\ &= \biggl( \frac{\displaystyle\sum_{i=0}^{n-1} \frac{1}{x_i}}{\displaystyle n} \biggr)^{-1}\end{align} ```
## Installation ```bash npm install @stdlib/stats-incr-hmean ``` 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 incrhmean = require( '@stdlib/stats-incr-hmean' ); ``` #### incrhmean() Returns an accumulator `function` which incrementally computes a [harmonic mean][harmonic-mean]. ```javascript var accumulator = incrhmean(); ``` #### accumulator( \[x] ) If provided an input value `x`, the accumulator function returns an updated [harmonic mean][harmonic-mean]. If not provided an input value `x`, the accumulator function returns the current [harmonic mean][harmonic-mean]. ```javascript var accumulator = incrhmean(); var v = accumulator( 2.0 ); // returns 2.0 v = accumulator( 1.0 ); // returns ~1.33 v = accumulator( 3.0 ); // returns ~1.64 v = accumulator(); // returns ~1.64 ```
## Notes - Input values are **not** type checked. If provided `NaN` or a value which, when used in computations, results in `NaN`, the accumulated value is `NaN` for **all** future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
## Examples ```javascript var randu = require( '@stdlib/random-base-randu' ); var incrhmean = require( '@stdlib/stats-incr-hmean' ); var accumulator; var v; var i; // Initialize an accumulator: accumulator = incrhmean(); // For each simulated datum, update the harmonic mean... for ( i = 0; i < 100; i++ ) { v = randu() * 100.0; accumulator( v ); } console.log( accumulator() ); ```
* * * ## See Also - [`@stdlib/stats-incr/gmean`][@stdlib/stats/incr/gmean]: compute a geometric mean incrementally. - [`@stdlib/stats-incr/mean`][@stdlib/stats/incr/mean]: compute an arithmetic mean incrementally. - [`@stdlib/stats-incr/mhmean`][@stdlib/stats/incr/mhmean]: compute a moving harmonic mean incrementally. - [`@stdlib/stats-incr/summary`][@stdlib/stats/incr/summary]: compute a statistical summary incrementally.
* * * ## 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-incr-hmean.svg [npm-url]: https://npmjs.org/package/@stdlib/stats-incr-hmean [test-image]: https://github.com/stdlib-js/stats-incr-hmean/actions/workflows/test.yml/badge.svg?branch=main [test-url]: https://github.com/stdlib-js/stats-incr-hmean/actions/workflows/test.yml?query=branch:main [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/stats-incr-hmean/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/stats-incr-hmean?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-incr-hmean/tree/deno [deno-readme]: https://github.com/stdlib-js/stats-incr-hmean/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/stats-incr-hmean/tree/umd [umd-readme]: https://github.com/stdlib-js/stats-incr-hmean/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/stats-incr-hmean/tree/esm [esm-readme]: https://github.com/stdlib-js/stats-incr-hmean/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/stats-incr-hmean/blob/main/branches.md [stdlib-license]: https://raw.githubusercontent.com/stdlib-js/stats-incr-hmean/main/LICENSE [harmonic-mean]: https://en.wikipedia.org/wiki/Harmonic_mean [@stdlib/stats/incr/gmean]: https://github.com/stdlib-js/stats-incr-gmean [@stdlib/stats/incr/mean]: https://github.com/stdlib-js/stats-incr-mean [@stdlib/stats/incr/mhmean]: https://github.com/stdlib-js/stats-incr-mhmean [@stdlib/stats/incr/summary]: https://github.com/stdlib-js/stats-incr-summary