pdf.js (1421B)
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 PINF = require( '@stdlib/constants/float64/pinf' ); 24 var isnan = require( '@stdlib/math/base/assert/is-nan' ); 25 26 27 // MAIN // 28 29 /** 30 * Evaluates the probability density function (PDF) for a degenerate distribution centered at `mu`. 31 * 32 * @param {number} x - input value 33 * @param {number} mu - constant value of the distribution 34 * @returns {number} evaluated probability density function 35 * 36 * @example 37 * var y = pdf( 2.0, 3.0 ); 38 * // returns 0.0 39 * 40 * @example 41 * var y = pdf( 3.0, 3.0 ); 42 * // returns Infinity 43 * 44 * @example 45 * var y = pdf( NaN, 0.0 ); 46 * // returns NaN 47 * 48 * @example 49 * var y = pdf( 0.0, NaN ); 50 * // returns NaN 51 */ 52 function pdf( x, mu ) { 53 if ( isnan( x ) || isnan( mu ) ) { 54 return NaN; 55 } 56 return ( x === mu ) ? PINF : 0.0; 57 } 58 59 60 // EXPORTS // 61 62 module.exports = pdf;