lgamma
gamma(x)Input: x · Output: no output
What it is
The gamma function (gamma(n) = (n-1)! for a positive integer n) and its natural log (lgamma(x) = ln|gamma(x)|). x is a real scalar, Vec, or Mat/Signal. Both have a pole at every non-positive integer (0, -1, -2, ...) — evaluating there is an error, not a silent inf/NaN.
Overloads
One call shape — this function is not overloaded.
| Code | Input | Output | Description |
gamma(x) | x scalar, Vec, Mat, or Signalnot documented yet | not documented yet | Both have a pole at every non-positive integer (0, -1, -2, ...) — evaluating there is an error, not a silent inf/NaN. |
Examples
No documentation example calls this form yet. The Core maths chapter is where one belongs.
How it works
lgamma(x) = ln|gamma(x)| -- same poles as gamma itself (ln of a pole is still a pole, not a large-but-finite number). libm::lgamma_r returns (ln|gamma(x)|, sign); only the magnitude is lgamma's contract here, matching every other language's lgamma.
From the note above this builtin in the interpreter, where the reasoning was written down as it was built.
See also
gamma — documented in the same entry.