85 lines
1.7 KiB
JavaScript
85 lines
1.7 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 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 ln = require( '@stdlib/math/base/special/ln' );
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var exp = require( '@stdlib/math/base/special/exp' );
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// MAIN //
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/**
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* Returns an accumulator function which incrementally computes a geometric mean.
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*
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* @returns {Function} accumulator function
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*
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* @example
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* var accumulator = incrgmean();
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*
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* var v = accumulator();
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* // returns null
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*
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* v = accumulator( 2.0 );
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* // returns 2.0
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*
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* v = accumulator( 5.0 );
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* // returns ~3.16
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*
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* v = accumulator();
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* // returns ~3.16
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*/
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function incrgmean() {
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var sum;
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var N;
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var v;
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sum = 0.0;
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N = 0;
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v = 1;
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return accumulator;
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/**
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* If provided a value, the accumulator function returns an updated geometric mean. If not provided a value, the accumulator function returns the current geometric mean.
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*
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* @private
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* @param {number} [x] - new value
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* @returns {(number|null)} geometric mean or null
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*/
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function accumulator( x ) {
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if ( arguments.length === 0 ) {
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if ( N === 0 ) {
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return null;
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}
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return v;
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}
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N += 1;
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sum += ln( x );
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v = exp( sum/N );
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return v;
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}
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}
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// EXPORTS //
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module.exports = incrgmean;
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