hypertune
Version:
[Hypertune](https://www.hypertune.com/) is the most flexible platform for feature flags, A/B testing, analytics and app configuration. Built with full end-to-end type-safety, Git-style version control and local, synchronous, in-memory flag evaluation. Opt
32 lines • 1.14 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.default = logbeta;
function logbeta(a, b) {
// Log Beta Function using the relationship with Gamma function
// ln(Beta(a,b)) = ln(Gamma(a)) + ln(Gamma(b)) - ln(Gamma(a+b))
return lnGamma(a) + lnGamma(b) - lnGamma(a + b);
}
// Efficient implementation of ln(Gamma(x)) using Lanczos approximation
function lnGamma(x) {
const p = [
676.5203681218851, -1259.1392167224028, 771.32342877765313,
-176.61502916214059, 12.507343278686905, -0.13857109526572012,
9.9843695780195716e-6, 1.5056327351493116e-7,
];
if (x < 0.5) {
return Math.log(Math.PI) - Math.log(Math.sin(Math.PI * x)) - lnGamma(1 - x);
}
// eslint-disable-next-line no-param-reassign
x -= 1;
const y = x + 7.5;
let sum = 0.99999999999980993;
// eslint-disable-next-line no-plusplus
for (let i = 0; i < p.length; i++) {
sum += p[i] / (x + i + 1);
}
return (Math.log(Math.sqrt(2 * Math.PI)) +
(x + 0.5) * Math.log(y) -
y +
Math.log(sum));
}
//# sourceMappingURL=logbeta.js.map