time-to-botec/js/node_modules/@stdlib/stats/incr/gmean/lib/main.js

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/**
* @license Apache-2.0
*
* Copyright (c) 2018 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 ln = require( '@stdlib/math/base/special/ln' );
var exp = require( '@stdlib/math/base/special/exp' );
// MAIN //
/**
* Returns an accumulator function which incrementally computes a geometric mean.
*
* @returns {Function} accumulator function
*
* @example
* var accumulator = incrgmean();
*
* var v = accumulator();
* // returns null
*
* v = accumulator( 2.0 );
* // returns 2.0
*
* v = accumulator( 5.0 );
* // returns ~3.16
*
* v = accumulator();
* // returns ~3.16
*/
function incrgmean() {
var sum;
var N;
var v;
sum = 0.0;
N = 0;
v = 1;
return accumulator;
/**
* 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.
*
* @private
* @param {number} [x] - new value
* @returns {(number|null)} geometric mean or null
*/
function accumulator( x ) {
if ( arguments.length === 0 ) {
if ( N === 0 ) {
return null;
}
return v;
}
N += 1;
sum += ln( x );
v = exp( sum/N );
return v;
}
}
// EXPORTS //
module.exports = incrgmean;