time-to-botec

Benchmark sampling in different programming languages
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skewness.js (1319B)

      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 sqrt = require( '@stdlib/math/base/special/sqrt' );
     25 
     26 
     27 // MAIN //
     28 
     29 /**
     30 * Returns the skewness of a Poisson distribution.
     31 *
     32 * @param {PositiveNumber} lambda - mean parameter
     33 * @returns {PositiveNumber} skewness
     34 *
     35 * @example
     36 * var v = skewness( 9.0 );
     37 * // returns ~0.33
     38 *
     39 * @example
     40 * var v = skewness( 1.0 );
     41 * // returns 1.0
     42 *
     43 * @example
     44 * var v = skewness( -0.2 );
     45 * // returns NaN
     46 *
     47 * @example
     48 * var v = skewness( NaN );
     49 * // returns NaN
     50 */
     51 function skewness( lambda ) {
     52 	if ( isnan( lambda ) || lambda <= 0.0 ) {
     53 		return NaN;
     54 	}
     55 	return 1.0 / sqrt( lambda );
     56 }
     57 
     58 
     59 // EXPORTS //
     60 
     61 module.exports = skewness;