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Microsoft website has an introduction on GAMMA function.

I could download it and have a look, it's a ".xlsx" file and the formula is shown as =_xlfn.GAMMA(2.5).

enter image description here

However, when I create a new excel ".xlsx" file, I can't use it, neither by write formula as =_xlfn.GAMMA(2.5)" or "=GAMMA(2.5). enter image description here

Did I missed something? Is there some library I shall register, like using Solver function?


@dave-rook is right.

I'm using Excel 2007. The msdn page says "GAMMA" function applies to Excel 2013, so the problem is the version.

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What version of Excel are you using? – Dave Aug 27 '13 at 15:16
youre right the function isnt included with the workbook. it does work on the embed spreadsheet on the web, but its not anywhere to find within the downloaded file itself. – Meehow Aug 27 '13 at 15:59
is there some library can do that? i know that excel can have plugin's.. – athos Aug 27 '13 at 16:16
up vote 0 down vote accepted

In excel 2003 and up you can use


For all positive values

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If GAMMALN is not available under your language settings, you may need to be using the following formula:

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This is better as a comment perhaps – Dave M Feb 8 '14 at 18:01

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