tricube.js (1357B)
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 abs = require( '@stdlib/math/base/special/abs' ); 24 var isnan = require( '@stdlib/assert/is-nan' ); 25 var pow = require( '@stdlib/math/base/special/pow' ); 26 27 28 // VARIABLES // 29 30 var LEADING_TERM = ( 70.0 / 81.0 ); 31 32 33 // MAIN // 34 35 /** 36 * Computes the tricube kernel for a value. 37 * 38 * @private 39 * @param {number} u - value for which we wish to calculate the tricube kernel 40 * @returns {number} the value for the kernel at u 41 * 42 * @example 43 * var u = 5; 44 * out = tricube(u); 45 * // returns 0 46 */ 47 function tricube(u) { 48 var absU; 49 50 if ( isnan( u ) ) { 51 return NaN; 52 } 53 absU = abs( u ); 54 if ( absU > 1.0 ) { 55 return 0.0; 56 } 57 return LEADING_TERM * pow( 1.0 - pow( absU, 3.0 ), 3.0 ); 58 } 59 60 61 // EXPORTS // 62 63 module.exports = tricube;