time-to-botec

Benchmark sampling in different programming languages
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variance.js (1402B)

      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 PINF = require( '@stdlib/constants/float64/pinf' );
     25 
     26 
     27 // MAIN //
     28 
     29 /**
     30 * Returns the variance of a Student's t distribution.
     31 *
     32 * @param {PositiveNumber} v - degrees of freedom
     33 * @returns {PositiveNumber} variance
     34 *
     35 * @example
     36 * var v = variance( 9.0 );
     37 * // returns ~1.286
     38 *
     39 * @example
     40 * var v = variance( 2.0 );
     41 * // returns Infinity
     42 *
     43 * @example
     44 * var v = variance( 0.5 );
     45 * // returns NaN
     46 *
     47 * @example
     48 * var v = variance( -0.2 );
     49 * // returns NaN
     50 *
     51 * @example
     52 * var v = variance( NaN );
     53 * // returns NaN
     54 */
     55 function variance( v ) {
     56 	if ( isnan( v ) || v <= 1.0 ) {
     57 		return NaN;
     58 	}
     59 	if ( v <= 2.0 ) {
     60 		return PINF;
     61 	}
     62 	return v / ( v - 2.0 );
     63 }
     64 
     65 
     66 // EXPORTS //
     67 
     68 module.exports = variance;