Notice: On March 31, it was **announced** that Statalist is moving from an email list to a **forum**. The old list will shut down on April 23, and its replacement, **statalist.org** is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

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

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

Date |
Thu, 13 May 2010 16:49:13 +0100 |

Fair enough. I am reminded of the old advice "To solve this differential equation, stare at it until a solution occurs to you". I was trying a sales pitch for -viewsource-. There is a downside: thinking is needed too. Also, experience helps and experiment helps a great deal. Consider the problem report: The program fails to satisfy if the argument is too big. So, something breaks down inside. Experience indicates the problem is likely to be an overflow or an underflow. The first thing in the program that looked as if could be problematic was calculating exp(-mean) (NOT exp(mean)). Experimentation with -display- brought confirmation. Nick n.j.cox@durham.ac.uk Martin Weiss " look at the code." I don`t get this: Which problem is solved by looking at the code here? I did earlier, and could not tell that the problem was with "exp(710)". Maybe that is just me, maybe not... Nick Cox As someone said, if all else fails, look at the code. -viewsource rndpoi- gets you there in one. Karen Wright Thank you very much for the help. >>> "Martin Weiss" <martin.weiss1@gmx.de> 13/05/2010 16:06 >>> " You need something with a better algorithm." -genpoisson-, as in -findit genpoisson, does not complain or behave weirdly: ************* clear* set obs 10000 genpoisson x, mu(710) su hist x ************* HTH Martin -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox Sent: Donnerstag, 13. Mai 2010 16:57 To: statalist@hsphsun2.harvard.edu Subject: st: RE: RE: RE: RE: Stata stuck in loop with -rndpoi-? 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/

**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>

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

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

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

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

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

- Prev by Date:
**RE: st: RE: margeff after the glm command** - Next by Date:
**Re: st: brrweight(), jkrweight(), and vce() options of svyset** - Previous by thread:
**st: RE: RE: RE: RE: RE: RE: RE: Stata stuck in loop with -rndpoi-?** - Next by thread:
**st: margeff after the glm command** - Index(es):