@stdlib/math-base-special-gammaincinv
Version:
Inverse incomplete gamma function.
65 lines (58 loc) • 2.06 kB
JavaScript
/**
* @license Apache-2.0
*
* Copyright (c) 2022 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.
*/
/* This is a generated file. Do not edit directly. */
;
// MAIN //
/**
* Evaluates a rational function, i.e., the ratio of two polynomials described by the coefficients stored in \\(P\\) and \\(Q\\).
*
* ## Notes
*
* - Coefficients should be sorted in ascending degree.
* - The implementation uses [Horner's rule][horners-method] for efficient computation.
*
* [horners-method]: https://en.wikipedia.org/wiki/Horner%27s_method
*
* @private
* @param {number} x - value at which to evaluate the rational function
* @returns {number} evaluated rational function
*/
function evalrational( x ) {
var ax;
var s1;
var s2;
if ( x === 0.0 ) {
return -0.0011481191232;
}
if ( x < 0.0 ) {
ax = -x;
} else {
ax = x;
}
if ( ax <= 1.0 ) {
s1 = -0.0011481191232 + (x * (-0.112850923276 + (x * (1.51623048511 + (x * (-0.218472031183 + (x * 0.0730002451555))))))); // eslint-disable-line max-len
s2 = 1.0 + (x * (14.2482206905 + (x * (69.7360396285 + (x * (218.938950816 + (x * 277.067027185))))))); // eslint-disable-line max-len
} else {
x = 1.0 / x;
s1 = 0.0730002451555 + (x * (-0.218472031183 + (x * (1.51623048511 + (x * (-0.112850923276 + (x * -0.0011481191232))))))); // eslint-disable-line max-len
s2 = 277.067027185 + (x * (218.938950816 + (x * (69.7360396285 + (x * (14.2482206905 + (x * 1.0))))))); // eslint-disable-line max-len
}
return s1 / s2;
}
// EXPORTS //
module.exports = evalrational;