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

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

Subject |
st: RE: RE: RE: RE: Stata stuck in loop with -rndpoi-? |

Date |
Thu, 13 May 2010 15:56:50 +0100 |

It's an underflow problem. -rndpoi- at one point calculates exp(-mean), but try . di exp(-710) and you will get 0. Even if you get results for means near 700, they will be of dubious accuracy. You need something with a better algorithm. Alternatively, won't a Poisson with mean 700 look pretty near Gaussian any way? I get the skewness and kurtosis to be . di 1/sqrt(700) .03779645 . di 3 + 1/700 3.0014286 which would cause broad and continuing smiles of pleasure in many branches of statistical science. Nick n.j.cox@durham.ac.uk Nick Cox What I said in 2003 still holds. Nick n.j.cox@durham.ac.uk Martin Weiss Also note Nick`s advice at http://www.stata.com/statalist/archive/2003-08/msg00197.html, though things may have changed materially in the meantime... Karen Wright Unfortunately my IT department has a problem with letting us upgrade Stata, they have to perform it and do not want to - which is why I was trying to do it without the ugrade. Thank you, I shall just have to pester them again! >>> "Martin Weiss" <martin.weiss1@gmx.de> 13/05/2010 14:59:48 >>> You could just upgrade for free to Stata 10.1, and use the -rpoisson()- function... Karen Wright I am attempting to generate 10000 random number based on a poisson distribution with mean from my data, using -rndpoi- (from ssc). I seem to encounter a problem when the mean is greater than 700. Would anyone be able to help me, either with an alternative method of producing the figures I need, or what I am currently doing wrong? ************************ *this works: rndpoi 10000 694.5 *this doesn't: rndpoi 10000 710 ************************ I am currently using Stata 10.0 on Windows. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: RE: RE: RE: RE: RE: Stata stuck in loop with -rndpoi-?***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**References**:**st: Stata stuck in loop with -rndpoi-?***From:*"Karen Wright" <Karen.Wright@icr.ac.uk>

**st: RE: Stata stuck in loop with -rndpoi-?***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**st: RE: Stata stuck in loop with -rndpoi-?***From:*"Karen Wright" <Karen.Wright@icr.ac.uk>

**st: RE: RE: Stata stuck in loop with -rndpoi-?***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**st: RE: RE: RE: Stata stuck in loop with -rndpoi-?***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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