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 81 82 83 84 85 86 | 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 215x 215x 215x 215x 204x 215x 15x 15x 200x 215x 1x 1x 1x 1x 1x | /**
* @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 isPositiveInteger = require( '@stdlib/math/base/assert/is-positive-integer' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var digamma = require( '@stdlib/math/base/special/digamma' );
var gamma = require( '@stdlib/math/base/special/gamma' );
var ln = require( '@stdlib/math/base/special/ln' );
// MAIN //
/**
* Returns the differential entropy of an Erlang distribution.
*
* @param {PositiveInteger} k - shape parameter
* @param {PositiveNumber} lambda - rate parameter
* @returns {number} differential entropy
*
* @example
* var v = entropy( 1, 1.0 );
* // returns 1.0
*
* @example
* var v = entropy( 4, 12.0 );
* // returns ~-0.462
*
* @example
* var v = entropy( 8, 2.0 );
* // returns ~1.723
*
* @example
* var v = entropy( 1.5, 2.0 );
* // returns NaN
*
* @example
* var v = entropy( 1, -0.1 );
* // returns NaN
*
* @example
* var v = entropy( -0.1, 1.0 );
* // returns NaN
*
* @example
* var v = entropy( 2, NaN );
* // returns NaN
*
* @example
* var v = entropy( NaN, 2.0 );
* // returns NaN
*/
function entropy( k, lambda ) {
if (
!isPositiveInteger( k ) ||
isnan( lambda ) ||
lambda <= 0.0
) {
return NaN;
}
return ( ( 1-k ) * digamma( k ) ) + ln( gamma( k ) / lambda ) + k;
}
// EXPORTS //
module.exports = entropy;
|