If your data are continuous but must be positive, consider a gamma or inverse gaussian glm.
If your data are non-negative (is positive but could include zeros), consider glms based on Tweedie distributions. See, for example: http://cran.ms.unimelb.edu.au/src/contrib/Descriptions/tweedie.html Tweedie distributions have variances of the form var[Y] = phi * mu^p for real p not in the interval (0,1). p=2 is the gamma case, p=0 the normal case, p=1 and phi=1 the Poisson case. But when 1 < p < 2, the distribution are defined on the non-negative reals (and in fact correspond to a Poisson sum of gamma distributions). P. On Thursday 22 February 2007 05:37, Jarrett Byrnes wrote: > A reviewer recently remarked to me that, due to my data being > constrained to not fall below zero, a generalized linear model with a > negative binomial error (or poisson) with a log link would be more > appropriate for fitting my model. I ran it in R with glm.nb() and > got results that matched just using lm on log transformed data pretty > well. However, R indicated some warnings. I checked warnings(), and > saw a list of warnings as follows: > > Warning messages: > 1: non-integer x = 0.254825 > > I got the same error when trying to use the poisson family. > > My data is indeed continuous, not discrete (lots of non-integers). > > Does this mean that the model was not fit properly? Was data dropped > when fitting the model? Is there an option to deal with this that I > have overlooked? It would seem all is in order, but i just wanted to > make sure. Thanks! > > Thanks. > > -Jarrett > > ______________________________________________ > [email protected] 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. -- Dr Peter Dunn | dunn <at> usq.edu.au Faculty of Sciences, USQ; http://www.sci.usq.edu.au/staff/dunn Aust. Centre for Sustainable Catchments: www.usq.edu.au/acsc This email (including any attached files) is confidential an...{{dropped}} ______________________________________________ [email protected] 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.
