3.0 KiB
3.0 KiB
title | id | localeTitle | challengeType |
---|---|---|---|
Gamma function | 5a23c84252665b21eecc7e76 | 5a23c84252665b21eecc7e76 | 5 |
Description
$ \ Gamma (x) = \ displaystyle \ int_0 ^ \ infty t ^ {x-1} e ^ {- t} dt $
Instructions
Tests
tests:
- text: <code>gamma</code> debe ser una función.
testString: 'assert(typeof gamma=="function","<code>gamma</code> should be a function.")'
- text: ' <code>gamma("+tests[0]+")</code> debe devolver un número.'
testString: 'assert(typeof gamma(tests[0])=="number","<code>gamma("+tests[0]+")</code> should return a number.")'
- text: ' <code>gamma("+tests[0]+")</code> debe devolver <code>"+results[0]+"</code> .'
testString: 'assert.equal(gamma(tests[0]),results[0],"<code>gamma("+tests[0]+")</code> should return <code>"+results[0]+"</code>.")'
- text: ' <code>gamma("+tests[1]+")</code> debe devolver <code>"+results[1]+"</code> .'
testString: 'assert.equal(gamma(tests[1]),results[1],"<code>gamma("+tests[1]+")</code> should return <code>"+results[1]+"</code>.")'
- text: ' <code>gamma("+tests[2]+")</code> debe devolver <code>"+results[2]+"</code> .'
testString: 'assert.equal(gamma(tests[2]),results[2],"<code>gamma("+tests[2]+")</code> should return <code>"+results[2]+"</code>.")'
- text: ' <code>gamma("+tests[3]+")</code> debe devolver <code>"+results[3]+"</code> .'
testString: 'assert.equal(gamma(tests[3]),results[3],"<code>gamma("+tests[3]+")</code> should return <code>"+results[3]+"</code>.")'
- text: ' <code>gamma("+tests[4]+")</code> debe devolver <code>"+results[4]+"</code> .'
testString: 'assert.equal(gamma(tests[4]),results[4],"<code>gamma("+tests[4]+")</code> should return <code>"+results[4]+"</code>.")'
Challenge Seed
function gamma (x) {
// Good luck!
}
After Test
console.info('after the test');
Solution
function gamma(x) {
var p = [0.99999999999980993, 676.5203681218851, -1259.1392167224028,
771.32342877765313, -176.61502916214059, 12.507343278686905,
-0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7
];
var g = 7;
if (x < 0.5) {
return Math.PI / (Math.sin(Math.PI * x) * gamma(1 - x));
}
x -= 1;
var a = p[0];
var t = x + g + 0.5;
for (var i = 1; i < p.length; i++) {
a += p[i] / (x + i);
}
var result=Math.sqrt(2 * Math.PI) * Math.pow(t, x + 0.5) * Math.exp(-t) * a;
return result;
}