[R] random generation for a quasi distribution

Spencer Graves spencer.graves at pdf.com
Sat Jun 10 22:29:04 CEST 2006

	  Any "quasi distribution" is not well defined, which is why it is 
called "qausi".  Users decide that its likelihood "looks like" some 
other distribution, e.g. a Poisson, but it is "overdispersed".

	  If you want to simulate a "quasi binomial", you have to select a 
plausible "overdispersion" mechanism.  You could for example decide that 
the Poisson parameter follows a lognormal or a gamma distribution.  Then 
simulate the lognormal or gamma random variables and use those to 
simulate the poisson.


 > set.seed(5)
 > (Lam <- rlnorm(2, sdlog=9))
[1] 5.168803e-04 2.576182e+05
 > rpois(2, Lam)
[1]      0 257885

	  hope this helps
	  Spencer Graves

hugues wrote:
> Dear R-Help,
> As with the rpois() function to generate random data for a poisson
> distribution, I need to generate random data for a quasi distribution with
> var=mu^2.
> Does anyone known how to do this? 
> Thanks in advance,
> 	[[alternative HTML version deleted]]
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

More information about the R-help mailing list