[R] How to avoid the NaN errors in dnbinom?

francogrex francogrex at mail.com
Wed Oct 24 12:33:25 CEST 2007

Thanks Jim, I corrected the error by avoiding negative K values: 

I am not sure about the general code to determine the parameters though,
sometimes it gives the expected values (determined in advance by rnbinom)
and sometimes it's way off.

jholtman wrote:
> Your problems is that your code is generating NaN and 'err' is set to
> NaN and therefore the 'while (err > eps)' fails since NaN is not a
> logical variable.
> You should learn to use debug or the browser.  I put the following
> statement in your code:
>         new.parms=c(k1,mu1,k2,mu2,prob)
>         err=max(abs((old.parms-new.parms)/new.parms))
>         if (is.nan(err)) browser()  # added statement
>         iter=iter+1
>     }
> that caught the error and the printed out the values of some of your
> objects:
> Called from: mixnbinom(y, 10, 7, 20, 12, 0.8)
> Browse[1]> old.parms
> [1]  8.233552e+00  5.225557e+00 -2.487524e+05  1.512247e+01  9.668136e-01
> Warning message:
> In dnbinom(x, size, prob, log) : NaNs produced
> Browse[1]> new.parms
> [1] NaN NaN NaN NaN NaN
> Browse[1]>
> This shows that 'new.parms' at that point was all NaN.  You need to
> check your logic since is does say that "In dnbinom(x, size, prob,
> log) : NaNs produced".

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