dnbinom unreliable for absurdly large "size" parameter

[Ben Bolker-3]

   Check it out:

curve(dnbinom(1,mu=0.5,size=x),log="x",from=1,to=1e18)
abline(h=dpois(1,lambda=0.5),col=2,lty=2)
text(1,dpois(1,lambda=0.5)+0.02,"Poisson",col=2,pos=4)

   I will take a look in the C code when I get
a chance to see if I can offer
a patch, but in the meantime wanted to alert people to
this "feature" ...  (it looks like I will have to go
through dnbinom and dbinom_raw to see where the problem
is ...)

    Ben Bolker




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