60 lines
1.4 KiB
JavaScript
60 lines
1.4 KiB
JavaScript
|
/**
|
||
|
|
* @license Apache-2.0
|
||
|
|
*
|
||
|
|
* Copyright (c) 2020 The Stdlib Authors.
|
||
|
|
*
|
||
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
* you may not use this file except in compliance with the License.
|
||
|
|
* You may obtain a copy of the License at
|
||
|
|
*
|
||
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
*
|
||
|
|
* Unless required by applicable law or agreed to in writing, software
|
||
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
* See the License for the specific language governing permissions and
|
||
|
|
* limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
'use strict';
|
||
|
|
|
||
|
|
// MODULES //
|
||
|
|
|
||
|
|
var gsumpw = require( '@stdlib/blas/ext/base/gsumpw' ).ndarray;
|
||
|
|
|
||
|
|
|
||
|
|
// MAIN //
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Computes the arithmetic mean of a strided array using pairwise summation.
|
||
|
|
*
|
||
|
|
* @param {PositiveInteger} N - number of indexed elements
|
||
|
|
* @param {NumericArray} x - input array
|
||
|
|
* @param {integer} stride - stride length
|
||
|
|
* @param {NonNegativeInteger} offset - starting index
|
||
|
|
* @returns {number} arithmetic mean
|
||
|
|
*
|
||
|
|
* @example
|
||
|
|
* 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 ];
|
||
|
|
* var N = floor( x.length / 2 );
|
||
|
|
*
|
||
|
|
* var v = meanpw( N, x, 2, 1 );
|
||
|
|
* // returns 1.25
|
||
|
|
*/
|
||
|
|
function meanpw( N, x, stride, offset ) {
|
||
|
|
if ( N <= 0 ) {
|
||
|
|
return NaN;
|
||
|
|
}
|
||
|
|
if ( N === 1 || stride === 0 ) {
|
||
|
|
return x[ offset ];
|
||
|
|
}
|
||
|
|
return gsumpw( N, x, stride, offset ) / N;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
// EXPORTS //
|
||
|
|
|
||
|
|
module.exports = meanpw;
|