time-to-botec

Benchmark sampling in different programming languages
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quantile.js (2049B)

      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 tan = require( '@stdlib/math/base/special/tan' );
     25 var PI = require( '@stdlib/constants/float64/pi' );
     26 
     27 
     28 // MAIN //
     29 
     30 /**
     31 * Evaluates the quantile function for a Cauchy distribution with location parameter `x0` and scale parameter `gamma` at a probability `p`.
     32 *
     33 * @param {Probability} p - input value
     34 * @param {number} x0 - location parameter
     35 * @param {PositiveNumber} gamma - scale parameter
     36 * @returns {number} evaluated quantile function
     37 *
     38 * @example
     39 * var y = quantile( 0.3, 2.0, 2.0 );
     40 * // returns ~0.547
     41 *
     42 * @example
     43 * var y = quantile( 0.8, 10, 2.0 );
     44 * // returns ~12.753
     45 *
     46 * @example
     47 * var y = quantile( 0.1, 10.0, 2.0 );
     48 * // returns ~3.845
     49 *
     50 * @example
     51 * var y = quantile( 1.1, 0.0, 1.0 );
     52 * // returns NaN
     53 *
     54 * @example
     55 * var y = quantile( -0.2, 0.0, 1.0 );
     56 * // returns NaN
     57 *
     58 * @example
     59 * var y = quantile( NaN, 0.0, 1.0 );
     60 * // returns NaN
     61 *
     62 * @example
     63 * var y = quantile( 0.0, NaN, 1.0 );
     64 * // returns NaN
     65 *
     66 * @example
     67 * var y = quantile( 0.0, 0.0, NaN );
     68 * // returns NaN
     69 *
     70 * @example
     71 * // Negative scale parameter:
     72 * var y = quantile( 0.5, 0.0, -1.0 );
     73 * // returns NaN
     74 */
     75 function quantile( p, x0, gamma ) {
     76 	if (
     77 		isnan( x0 ) ||
     78 		isnan( gamma ) ||
     79 		gamma <= 0.0 ||
     80 		isnan( p ) ||
     81 		p < 0.0 ||
     82 		p > 1.0
     83 	) {
     84 		return NaN;
     85 	}
     86 	return x0 + ( gamma * tan( PI*( p-0.5 ) ) );
     87 }
     88 
     89 
     90 // EXPORTS //
     91 
     92 module.exports = quantile;