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From |
"Carlo Lazzaro" <carlo.lazzaro@tin.it> |

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

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

Date |
Fri, 7 Mar 2008 19:14:12 +0100 |

Dear Tiago, I would suggest you to take a look at what follows: ------------------------------------------------------ http://www.stata.com/help.cgi?density+functions gammap(a,x) Domain a: 1e-10 to 1e+17 Domain x: -8e+307 to 8e+307 Interesting domain is x > 0 Range: 0 to 1 Description: returns the cumulative gamma distribution with shape parameter a. returns 0 if x < 0. The cumulative Poisson (the probability of observing k or fewer events if the expected is x) can be evaluated as 1-gammap(k+1,x). The reverse cumulative (the probability of observing k or more events) can be evaluated as gammap(k,x). **************************************************************************** gammap() is also known as the incomplete gamma function (ratio). **************************************************************************** Probabilities for the three-parameter gamma distribution (see gammaden() can be calculated by shifting and scaling x; i.e., gammap(a,(x - g)/b). ------------------------------------------------------------------------- Kind Regards, Carlo -----Messaggio originale----- Da: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di tiago.pereira@incor.usp.br Inviato: venerd́ 7 marzo 2008 17.50 A: statalist@hsphsun2.harvard.edu Oggetto: st: Gamma functions in R and Stata's Gamma Functions Dear All, 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? Thanks in advance for your time. Tiago * * 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/ * * 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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