time-to-botec

Benchmark sampling in different programming languages
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pdf.js (2038B)

      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 isnan = require( '@stdlib/math/base/assert/is-nan' );
     24 var cospi = require( '@stdlib/math/base/special/cospi' );
     25 var PINF = require( '@stdlib/constants/float64/pinf' );
     26 
     27 
     28 // MAIN //
     29 
     30 /**
     31 * Evaluates the probability density function (PDF) for a raised cosine distribution with location parameter `mu` and scale parameter `s` at a value `x`.
     32 *
     33 * @param {number} x - input value
     34 * @param {number} mu - location parameter
     35 * @param {NonNegativeNumber} s - scale parameter
     36 * @returns {number} evaluated PDF
     37 *
     38 * @example
     39 * var y = pdf( 2.0, 0.0, 3.0 );
     40 * // returns ~0.083
     41 *
     42 * @example
     43 * var y = pdf( 2.5, 4.0, 2.0 );
     44 * // returns ~0.073
     45 *
     46 * @example
     47 * var y = pdf( NaN, 0.0, 1.0 );
     48 * // returns NaN
     49 *
     50 * @example
     51 * var y = pdf( 0.0, NaN, 1.0 );
     52 * // returns NaN
     53 *
     54 * @example
     55 * var y = pdf( 0.0, 0.0, NaN );
     56 * // returns NaN
     57 *
     58 * @example
     59 * // Negative scale parameter:
     60 * var y = pdf( 2.0, 0.0, -1.0 );
     61 * // returns NaN
     62 *
     63 * @example
     64 * var y = pdf( 2.0, 8.0, 0.0 );
     65 * // returns 0.0
     66 *
     67 * @example
     68 * var y = pdf( 8.0, 8.0, 0.0 );
     69 * // returns Infinity
     70 */
     71 function pdf( x, mu, s ) {
     72 	var z;
     73 	if (
     74 		isnan( x ) ||
     75 		isnan( mu ) ||
     76 		isnan( s ) ||
     77 		s < 0.0
     78 	) {
     79 		return NaN;
     80 	}
     81 	if ( s === 0.0 ) {
     82 		return ( x === mu ) ? PINF : 0.0;
     83 	}
     84 	if (
     85 		x < mu - s ||
     86 		x > mu + s
     87 	) {
     88 		return 0.0;
     89 	}
     90 	z = ( x - mu ) / s;
     91 	return ( 1.0 + cospi( z ) ) / ( 2.0 * s );
     92 }
     93 
     94 
     95 // EXPORTS //
     96 
     97 module.exports = pdf;