Calculate the arithmetic mean of a single-precision floating-point strided array using a two-pass error correction algorithm.
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> Calculate the [arithmetic mean][arithmetic-mean] of a single-precision floating-point strided array using a two-pass error correction algorithm.
The [arithmetic mean][arithmetic-mean] is defined as
``bash`
npm install @stdlib/stats-strided-smeanpn
`javascript`
var smeanpn = require( '@stdlib/stats-strided-smeanpn' );
#### smeanpn( N, x, strideX )
Computes the [arithmetic mean][arithmetic-mean] of a single-precision floating-point strided array using a two-pass error correction algorithm.
`javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );
var v = smeanpn( x.length, x, 1 );
// returns ~0.3333
`
The function has the following parameters:
- N: number of indexed elements.
- x: input [Float32Array][@stdlib/array/float32].x
- strideX: stride length for .
The N and stride parameters determine which elements in the strided array are accessed at runtime. For example, to compute the [arithmetic mean][arithmetic-mean] of every other element in x,
`javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var v = smeanpn( 4, x, 2 );
// returns 1.25
`
Note that indexing is relative to the first index. To introduce an offset, use [typed array][mdn-typed-array] views.
`javascript
var Float32Array = require( '@stdlib/array-float32' );
var x0 = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var v = smeanpn( 4, x1, 2 );
// returns 1.25
`
#### smeanpn.ndarray( N, x, strideX, offsetX )
Computes the [arithmetic mean][arithmetic-mean] of a single-precision floating-point strided array using a two-pass error correction algorithm and alternative indexing semantics.
`javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ 1.0, -2.0, 2.0 ] );
var v = smeanpn.ndarray( x.length, x, 1, 0 );
// returns ~0.33333
`
The function has the following additional parameters:
- offsetX: 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 [arithmetic mean][arithmetic-mean] for every other element in x starting from the second element
`javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var v = smeanpn.ndarray( 4, x, 2, 1 );
// returns 1.25
`
- If N <= 0, both functions return NaN.
`javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var smeanpn = require( '@stdlib/stats-strided-smeanpn' );
var x = discreteUniform( 10, -50, 50, {
'dtype': 'float32'
});
console.log( x );
var v = smeanpn( x.length, x, 1 );
console.log( v );
`
*
`c`
#include "stdlib/stats/strided/smeanpn.h"
#### stdlib_strided_smeanpn( N, \*X, strideX )
Computes the [arithmetic mean][arithmetic-mean] of a single-precision floating-point strided array using a two-pass error correction algorithm.
`c
const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
float v = stdlib_strided_smeanpn( 4, x, 2 );
// returns 4.0f
`
The function accepts the following arguments:
- N: [in] CBLAS_INT number of indexed elements.[in] float*
- X: input array.[in] CBLAS_INT
- strideX: stride length for X.
`c`
float stdlib_strided_smeanpn( const CBLAS_INT N, const float *X, const CBLAS_INT strideX );
#### stdlib_strided_smeanpn_ndarray( N, \*X, strideX, offsetX )
Computes the [arithmetic mean][arithmetic-mean] of a single-precision floating-point strided array using a two-pass error correction algorithm and alternative indexing semantics.
`c
const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
float v = stdlib_strided_smeanpn_ndarray( 4, x, 2, 0 );
// returns 4.0f
`
The function accepts the following arguments:
- N: [in] CBLAS_INT number of indexed elements.[in] float*
- X: input array.[in] CBLAS_INT
- strideX: stride length for X.[in] CBLAS_INT
- offsetX: starting index for X.
`c`
float stdlib_strided_smeanpn_ndarray( const CBLAS_INT N, const float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
`c
#include "stdlib/stats/strided/smeanpn.h"
#include
int main( void ) {
// Create a strided array:
const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
// Specify the number of elements:
const int N = 4;
// Specify the stride length:
const int strideX = 2;
// Compute the arithmetic mean:
float v = stdlib_strided_smeanpn( N, x, strideX );
// Print the result:
printf( "mean: %f\n", v );
}
`
*
- Neely, Peter M. 1966. "Comparison of Several Algorithms for Computation of Means, Standard Deviations and Correlation Coefficients." _Communications of the ACM_ 9 (7). Association for Computing Machinery: 496–99. doi:[10.1145/365719.365958][@neely:1966a].
- Schubert, Erich, and Michael Gertz. 2018. "Numerically Stable Parallel Computation of (Co-)Variance." In _Proceedings of the 30th International Conference on Scientific and Statistical Database Management_. New York, NY, USA: Association for Computing Machinery. doi:[10.1145/3221269.3223036][@schubert:2018a].
*
- [@stdlib/stats-strided/dmeanpn][@stdlib/stats/strided/dmeanpn]: calculate the arithmetic mean of a double-precision floating-point strided array using a two-pass error correction algorithm.
- [@stdlib/stats-strided/meanpn][@stdlib/stats/strided/meanpn]: calculate the arithmetic mean of a strided array using a two-pass error correction algorithm.
- [@stdlib/stats-strided/smean][@stdlib/stats/strided/smean]: calculate the arithmetic mean of a single-precision floating-point strided array.
- [@stdlib/stats-strided/snanmeanpn][@stdlib/stats/strided/snanmeanpn]: calculate the arithmetic mean of a single-precision floating-point strided array, ignoring NaN values and using a two-pass error correction algorithm.
*
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].
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---
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Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[umd]: https://github.com/umdjs/umd
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[deno-url]: https://github.com/stdlib-js/stats-strided-smeanpn/tree/deno
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[umd-url]: https://github.com/stdlib-js/stats-strided-smeanpn/tree/umd
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[arithmetic-mean]: https://en.wikipedia.org/wiki/Arithmetic_mean
[@stdlib/array/float32]: https://www.npmjs.com/package/@stdlib/array-float32
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[@neely:1966a]: https://doi.org/10.1145/365719.365958
[@schubert:2018a]: https://doi.org/10.1145/3221269.3223036
[@stdlib/stats/strided/dmeanpn]: https://www.npmjs.com/package/@stdlib/stats-strided-dmeanpn
[@stdlib/stats/strided/meanpn]: https://www.npmjs.com/package/@stdlib/stats-strided-meanpn
[@stdlib/stats/strided/smean]: https://www.npmjs.com/package/@stdlib/stats-strided-smean
[@stdlib/stats/strided/snanmeanpn]: https://www.npmjs.com/package/@stdlib/stats-strided-snanmeanpn