69 lines
2.0 KiB
JavaScript
69 lines
2.0 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2020 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var dsumkbn = require( '@stdlib/blas/ext/base/dsumkbn' ).ndarray;
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// MAIN //
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/**
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* Computes the arithmetic mean of a double-precision floating-point strided array using an improved Kahan–Babuška algorithm.
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*
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* ## Method
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*
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* - This implementation uses an "improved Kahan–Babuška algorithm", as described by Neumaier (1974).
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*
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* ## References
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*
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* - 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](https://doi.org/10.1002/zamm.19740540106).
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*
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* @param {PositiveInteger} N - number of indexed elements
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* @param {Float64Array} x - input array
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* @param {integer} stride - stride length
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* @param {NonNegativeInteger} offset - starting index
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* @returns {number} arithmetic mean
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*
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* @example
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* var Float64Array = require( '@stdlib/array/float64' );
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* var floor = require( '@stdlib/math/base/special/floor' );
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*
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* var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
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* var N = floor( x.length / 2 );
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*
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* var v = dmeankbn( N, x, 2, 1 );
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* // returns 1.25
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*/
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function dmeankbn( N, x, stride, offset ) {
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if ( N <= 0 ) {
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return NaN;
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}
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if ( N === 1 || stride === 0 ) {
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return x[ offset ];
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}
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return dsumkbn( N, x, stride, offset ) / N;
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}
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// EXPORTS //
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module.exports = dmeankbn;
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