Syntax
GAMMALN.PRECISE(x)
| Parameter | Description |
|---|---|
| x | Parameter of the GAMMALN.PRECISE function. |
Examples
Equivalent to GAMMALN
Formula
=GAMMALN.PRECISE(10)
Returns ~12.8018. This equals LN(9!) = LN(362880) = 12.8018, identical to GAMMALN(10).
Small positive value
Formula
=GAMMALN.PRECISE(0.01)
Returns ~4.5995. The gamma function gets very large near zero, so its log is still manageable.
Large argument
Formula
=GAMMALN.PRECISE(200)
Returns ~857.934. Direct computation of gamma(200) would overflow, but the log-gamma is a reasonable number.
Common Errors
#NUM!
x must be positive. Zero and negative values are not in the domain of the gamma function.
#VALUE!
Occurs when the argument is non-numeric.
Tips
Identical to GAMMALN
In practice, GAMMALN and GAMMALN.PRECISE produce the same results. Use whichever is consistent with your spreadsheet's naming conventions.
When to use this
GAMMALN.PRECISE is primarily useful for building custom distribution functions or computing probabilities that involve the gamma function in their formulas.
Stirling's approximation check
For large x, GAMMALN(x) is approximately (x-0.5)*LN(x) - x + 0.5*LN(2*PI()). This can serve as a sanity check for your results.
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