Hi, Use offset variables if count occurrences of an event and you want to model the observation time.
glm(count ~ predictors + offset(log(observation_time)), family=poisson) If you want to compare durations, look at library(survival), ?coxph If tnoise_sqrt is the square root of tourist noise, your example seems incorrect, because it is a predictor, not the dependent variable tnoise_sqrt ~ lengthfeeding_log Best wishes, Matthias Am 30.12.2011 16:29, schrieb Lucy Dablin: > Great lists, I always find them useful, thank you to > everyone who contributes to them. > > > My question is regarding non-integer values from some data I > collected on parrots when using the poisson GLM. I observed the parrots on a > daily basis to see if they were affected by tourist presence. My key > predictors > are tourist noise (averaged over a day period so decimal value, square root to > adjust for skew), tourist number (the > number of tourists at a site, square root), and the number of boats passing > the > site in a day (log). These are compared with predictors: total number of birds > (count data, square root), average time devoted to foraging at site (log), > species > richness (sqrt), and the number of flushes per day. Apart from the last one > they are all non-integer values. When I run a glm for example: > > > parrots<- glm(tnoise_sqrt ~ lengthfeeding_log, family = > poisson) > > summary(parrots) > > > There are warnings which are "27: In dpois(y, mu, log = > TRUE) : non-integer x = 1.889822" I was advised to use the offset() function > however this does not seem to correct the problem and I find the code > confusing. > What GLM approach should I be using for multiple non-integer predictors and > non-integer responses? Does my GLM approach seem appropriate? > Thank you for taking the time to consider this. > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] ______________________________________________ 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.
