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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: Gamma functions in R and Stata's Gamma Functions |

Date |
Fri, 7 Mar 2008 18:55:36 -0000 |

Tiago gave only part of the specification for R's =pgamma()= (as nonce notation =function()= refers to R functions, to correspond to -function()- for Stata functions.) =pgamma()= allows you to specify rate or scale. They are reciprocals. So scale = 1/rate, rate = 1/scale. The nearest equivalent is Stata's -gammap()-. Stata uses the notation gammap(a, x). Here a is the shape parameter, x is the value. So where is the scale (or rate) parameter? Essentially you provide it like this: gammap(a, x / scale) or like this: gammap(a, rate * x) For an example within a Stata program, look inside -pgamma.ado- from SSC. Nick n.j.cox@durham.ac.uk tiago.pereira@incor.usp.br I am trying to implement a test that requires the incomplete gamma function. The R code is given by example<- pgamma(Z, shape=X,rate=Y) where Z is the critical value for a chi^2 distribution. I am not very experienced with this distribution, and failed to find out the corresponding counterpart in Stata. Hence, would it be possivle to you to provide me some tips to implement it in Stata? * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Gamma functions in R and Stata's Gamma Functions***From:*tiago.pereira@incor.usp.br

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