main.js (3759B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive; 24 var isnan = require( '@stdlib/math/base/assert/is-nan' ); 25 var PINF = require( '@stdlib/constants/float64/pinf' ); 26 var NINF = require( '@stdlib/constants/float64/ninf' ); 27 var Float64Array = require( '@stdlib/array/float64' ); 28 29 30 // MAIN // 31 32 /** 33 * Returns an accumulator function which incrementally computes a moving mid-range. 34 * 35 * @param {PositiveInteger} W - window size 36 * @throws {TypeError} must provide a positive integer 37 * @returns {Function} accumulator function 38 * 39 * @example 40 * var accumulator = incrmmidrange( 3 ); 41 * 42 * var mr = accumulator(); 43 * // returns null 44 * 45 * mr = accumulator( 2.0 ); 46 * // returns 2.0 47 * 48 * mr = accumulator( -5.0 ); 49 * // returns -1.5 50 * 51 * mr = accumulator( 3.0 ); 52 * // returns -1.0 53 * 54 * mr = accumulator( 5.0 ); 55 * // returns 0.0 56 * 57 * mr = accumulator(); 58 * // returns 0.0 59 */ 60 function incrmmidrange( W ) { 61 var buf; 62 var min; 63 var max; 64 var N; 65 var i; 66 if ( !isPositiveInteger( W ) ) { 67 throw new TypeError( 'invalid argument. Must provide a positive integer. Value: `' + W + '`.' ); 68 } 69 buf = new Float64Array( W ); 70 min = PINF; 71 max = NINF; 72 i = -1; 73 N = 0; 74 75 return accumulator; 76 77 /** 78 * If provided a value, the accumulator function returns an updated mid-range. If not provided a value, the accumulator function returns the current mid-range. 79 * 80 * @private 81 * @param {number} [x] - input value 82 * @returns {(number|null)} mid-range or null 83 */ 84 function accumulator( x ) { 85 var v; 86 var k; 87 if ( arguments.length === 0 ) { 88 if ( N === 0 ) { 89 return null; 90 } 91 return ( max+min ) / 2.0; 92 } 93 // Update the index for managing the circular buffer: 94 i = (i+1) % W; 95 96 if ( x === 0.0 ) { 97 x = 0.0; // normalizes +-0 98 } 99 // Case: incoming value is NaN... 100 if ( isnan( x ) ) { 101 N = W; // explicitly set to avoid `N < W` branch 102 min = x; 103 max = x; 104 } 105 // Case: initial window... 106 else if ( N < W ) { 107 N += 1; 108 if ( x < min ) { 109 min = x; 110 } 111 if ( x > max ) { 112 max = x; 113 } 114 } 115 // Case: outgoing value is the current minimum or maximum and the new value is either greater than the minimum or less than the maximum, and, thus, we need to find new accumulated values among the current buffer values... 116 else if ( 117 ( buf[ i ] === min && x > min ) || 118 ( buf[ i ] === max && x < max ) || 119 isnan( buf[ i ] ) 120 ) { 121 min = x; 122 max = x; 123 for ( k = 0; k < W; k++ ) { 124 if ( k !== i ) { 125 v = buf[ k ]; 126 if ( isnan( v ) ) { 127 min = v; 128 max = v; 129 break; // no need to continue searching 130 } 131 if ( v < min ) { 132 min = v; 133 } 134 if ( v > max ) { 135 max = v; 136 } 137 } 138 } 139 } 140 // Case: incoming value is less than current minimum value... 141 else if ( x < min ) { 142 min = x; 143 } 144 // Case: incoming value is greater than current maximum value... 145 else if ( x > max ) { 146 max = x; 147 } 148 // Case: updating existing window; however, the minimum and maximum values do not change so nothing to do but update our buffer... 149 buf[ i ] = x; 150 151 return ( max+min ) / 2.0; 152 } 153 } 154 155 156 // EXPORTS // 157 158 module.exports = incrmmidrange;