time-to-botec

Benchmark sampling in different programming languages
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pdf.js (2017B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2020 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/math/base/assert/is-positive-integer' );
     24 var isfinite = require( '@stdlib/math/base/assert/is-finite' );
     25 var isnan = require( '@stdlib/math/base/assert/is-nan' );
     26 var exp = require( '@stdlib/math/base/special/exp' );
     27 var ln = require( '@stdlib/math/base/special/ln' );
     28 var LN2 = require( '@stdlib/constants/float64/ln-two' );
     29 var weights = require( './weights.js' );
     30 
     31 
     32 // MAIN //
     33 
     34 /**
     35 * Evaluates the probability density function (PDF) of the Wilcoxon signed rank test statistic with `n` observations.
     36 *
     37 * @param {number} x - input value
     38 * @param {PositiveInteger} n - number of observations
     39 * @returns {Probability} evaluated PDF
     40 *
     41 * @example
     42 * var y = pdf( 7.0, 9 );
     43 * // returns ~0.01
     44 *
     45 * @example
     46 * var y = pdf( 7.0, 6 );
     47 * // returns ~0.063
     48 *
     49 * @example
     50 * var y = pdf( -1.0, 40 );
     51 * // returns 0.0
     52 *
     53 * @example
     54 * var y = pdf( NaN, 10 );
     55 * // returns NaN
     56 *
     57 * @example
     58 * var y = pdf( 0.0, NaN );
     59 * // returns NaN
     60 *
     61 * @example
     62 * var y = pdf( 2.0, -1 );
     63 * // returns NaN
     64 *
     65 * @example
     66 * var y = pdf( 2.0, 1.8 );
     67 * // returns NaN
     68 */
     69 function pdf( x, n ) {
     70 	var mlim;
     71 	if (
     72 		isnan( x ) ||
     73 		!isPositiveInteger( n ) ||
     74 		!isfinite( n )
     75 	) {
     76 		return NaN;
     77 	}
     78 	mlim = ( n * ( n + 1 ) ) / 2;
     79 	if ( x < 0.0 || x > mlim ) {
     80 		return 0.0;
     81 	}
     82 	return exp( ln( weights( x, n ) ) - ( n * LN2 ) );
     83 }
     84 
     85 
     86 // EXPORTS //
     87 
     88 module.exports = pdf;