var(y) = mu + mu^2/theta where E(y) = mu. best, Simon
On 13/11/13 10:38, Mark Payne wrote:
Dear R-help, The negative binomial distribution has several different parameterisations, but I can't seem to figure out what the exact one used in mgcv's negbin family is? negbin() requires a theta argument, but its not clear anywhere in the documentation (that I can find), how this parameter should be interpreted - for example, can it be less than 1? Best wishes, MArk ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
-- Simon Wood, Mathematical Science, University of Bath BA2 7AY UK +44 (0)1225 386603 http://people.bath.ac.uk/sw283 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
