81 lines
1.6 KiB
JavaScript
81 lines
1.6 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 floor = require( '@stdlib/math/base/special/floor' );
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// FUNCTIONS //
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/**
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* Comparator function used to sort values in ascending order.
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*
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* @private
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* @param {number} a - first number
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* @param {number} b - second number
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* @returns {number} difference between `a` and `b`
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*/
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function ascending( a, b ) {
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return a - b;
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}
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// MAIN //
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/**
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* Computes the median of an array.
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*
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* @param {Array} arr - input array
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* @returns {number} median value
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*/
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function median( arr ) {
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var len = arr.length;
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var id;
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var d;
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var i;
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if ( !len ) {
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return null;
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}
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// Copy and sort data in ascending order:
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d = [];
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for ( i = 0; i < len; i++ ) {
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d.push( arr[ i ] );
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}
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d.sort( ascending );
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// Get the middle index:
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id = floor( len / 2 );
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if ( len % 2 ) {
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// The number of elements is not evenly divisible by two, hence we have a middle index:
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return d[ id ];
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}
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// Even number of elements, so must take the mean of the two middle values:
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return ( d[ id-1 ] + d[ id ] ) / 2.0;
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}
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// EXPORTS //
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module.exports = median;
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