Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 | 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 4012x 4012x 4012x 4012x 4012x 4x 4x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4008x 4011x 2x 2x 4009x 4011x 4012x 3x 3x 3x 3x 3x | /**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var constantFunction = require( '@stdlib/utils/constant-function' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var beta = require( '@stdlib/math/base/special/beta' );
var sqrt = require( '@stdlib/math/base/special/sqrt' );
var pow = require( '@stdlib/math/base/special/pow' );
// MAIN //
/**
* Returns a function for evaluating the probability density function (PDF) for a Student's t distribution with `v` degrees of freedom.
*
* @param {PositiveNumber} v - degrees of freedom
* @returns {Function} PDF
*
* @example
* var pdf = factory( 1.0 );
* var y = pdf( 3.0 );
* // returns ~0.032
*
* y = pdf( 1.0 );
* // returns ~0.159
*/
function factory( v ) {
var exponent;
var betaTerm;
if ( isnan( v ) || v <= 0 ) {
return constantFunction( NaN );
}
betaTerm = sqrt( v ) * beta( v/2.0, 0.5 );
exponent = ( 1.0 + v ) / 2.0;
return pdf;
/**
* Evaluates the probability density function (PDF) for a Student's t distribution.
*
* @private
* @param {number} x - input value
* @returns {number} evaluated PDF
*
* @example
* var y = pdf( 2.3 );
* // returns <number>
*/
function pdf( x ) {
if ( isnan( x ) ) {
return NaN;
}
return pow( v / ( v + pow( x, 2.0 ) ), exponent ) / betaTerm;
}
}
// EXPORTS //
module.exports = factory;
|