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https://github.com/stdlib-js/blas-ext-base-gnansumkbn

Calculate the sum of strided array elements, ignoring NaN values and using an improved Kahan–Babuška algorithm.
https://github.com/stdlib-js/blas-ext-base-gnansumkbn

array blas compensated extended javascript kahan kbn math mathematics node node-js nodejs statistics stats stdlib strided strided-array sum summation total

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Calculate the sum of strided array elements, ignoring NaN values and using an improved Kahan–Babuška algorithm.

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README 

        



  

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# gnansumkbn



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



> Calculate the sum of strided array elements, ignoring `NaN` values and using an improved Kahan–Babuška algorithm.



## Installation



```bash

npm install @stdlib/blas-ext-base-gnansumkbn

```



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 gnansumkbn = require( '@stdlib/blas-ext-base-gnansumkbn' );

```



#### gnansumkbn( N, x, stride )



Computes the sum of strided array elements, ignoring `NaN` values and using an improved Kahan–Babuška algorithm.



```javascript

var x = [ 1.0, -2.0, NaN, 2.0 ];

var N = x.length;



var v = gnansumkbn( N, x, 1 );

// returns 1.0

```



The function has the following parameters:



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

-   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].

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



The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to compute the sum of every other element in `x`,



```javascript

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



var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0, NaN, NaN ];

var N = floor( x.length / 2 );



var v = gnansumkbn( N, x, 2 );

// returns 5.0

```



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 = gnansumkbn( N, x1, 2 );

// returns 5.0

```



#### gnansumkbn.ndarray( N, x, stride, offset )



Computes the sum of strided array elements, ignoring `NaN` values and using an improved Kahan–Babuška algorithm and alternative indexing semantics.



```javascript

var x = [ 1.0, -2.0, NaN, 2.0 ];

var N = x.length;



var v = gnansumkbn.ndarray( N, x, 1, 0 );

// returns 1.0

```



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 sum of every other value in `x` starting from the second value



```javascript

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



var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0, NaN, NaN ];

var N = floor( x.length / 2 );



var v = gnansumkbn.ndarray( N, x, 2, 1 );

// returns 5.0

```



## Notes



-   If `N <= 0`, both functions return `0.0`.

-   Depending on the environment, the typed versions ([`dnansumkbn`][@stdlib/blas/ext/base/dnansumkbn], [`snansumkbn`][@stdlib/blas/ext/base/snansumkbn], etc.) are likely to be significantly more performant.



## Examples



```javascript

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

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

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

var gnansumkbn = require( '@stdlib/blas-ext-base-gnansumkbn' );



var x;

var i;



x = new Float64Array( 10 );

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

    if ( randu() < 0.2 ) {

        x[ i ] = NaN;

    } else {

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

    }

}

console.log( x );



var v = gnansumkbn( x.length, x, 1 );

console.log( v );

```



* * *



## References



-   Neumaier, Arnold. 1974. "Rounding Error Analysis of Some Methods for Summing Finite Sums." _Zeitschrift Für Angewandte Mathematik Und Mechanik_ 54 (1): 39–51. doi:[10.1002/zamm.19740540106][@neumaier:1974a].



* * *



## See Also



-   [`@stdlib/blas-ext/base/dnansumkbn`][@stdlib/blas/ext/base/dnansumkbn]: calculate the sum of double-precision floating-point strided array elements, ignoring NaN values and using an improved Kahan–Babuška algorithm.

-   [`@stdlib/blas-ext/base/gnansum`][@stdlib/blas/ext/base/gnansum]: calculate the sum of strided array elements, ignoring NaN values.

-   [`@stdlib/blas-ext/base/gnansumkbn2`][@stdlib/blas/ext/base/gnansumkbn2]: calculate the sum of strided array elements, ignoring NaN values and using a second-order iterative Kahan–Babuška algorithm.

-   [`@stdlib/blas-ext/base/gnansumors`][@stdlib/blas/ext/base/gnansumors]: calculate the sum of strided array elements, ignoring NaN values and using ordinary recursive summation.

-   [`@stdlib/blas-ext/base/gnansumpw`][@stdlib/blas/ext/base/gnansumpw]: calculate the sum of strided array elements, ignoring NaN values and using pairwise summation.

-   [`@stdlib/blas-ext/base/gsumkbn`][@stdlib/blas/ext/base/gsumkbn]: calculate the sum of strided array elements using an improved Kahan–Babuška algorithm.

-   [`@stdlib/blas-ext/base/snansumkbn`][@stdlib/blas/ext/base/snansumkbn]: calculate the sum of single-precision floating-point strided array elements, ignoring NaN values and using an improved Kahan–Babuška algorithm.



* * *



## 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/blas-ext-base-gnansumkbn.svg

[npm-url]: https://npmjs.org/package/@stdlib/blas-ext-base-gnansumkbn



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

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



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

[coverage-url]: https://codecov.io/github/stdlib-js/blas-ext-base-gnansumkbn?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/blas-ext-base-gnansumkbn/tree/deno

[deno-readme]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn/tree/umd

[umd-readme]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn/tree/esm

[esm-readme]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ext-base-gnansumkbn/main/LICENSE



[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array



[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray



[@neumaier:1974a]: https://doi.org/10.1002/zamm.19740540106



[@stdlib/blas/ext/base/dnansumkbn]: https://github.com/stdlib-js/blas-ext-base-dnansumkbn



[@stdlib/blas/ext/base/snansumkbn]: https://github.com/stdlib-js/blas-ext-base-snansumkbn



[@stdlib/blas/ext/base/gnansum]: https://github.com/stdlib-js/blas-ext-base-gnansum



[@stdlib/blas/ext/base/gnansumkbn2]: https://github.com/stdlib-js/blas-ext-base-gnansumkbn2



[@stdlib/blas/ext/base/gnansumors]: https://github.com/stdlib-js/blas-ext-base-gnansumors



[@stdlib/blas/ext/base/gnansumpw]: https://github.com/stdlib-js/blas-ext-base-gnansumpw



[@stdlib/blas/ext/base/gsumkbn]: https://github.com/stdlib-js/blas-ext-base-gsumkbn