Hello useRs! I have % cover data for different plant species in 300 plots, and I use the ARCSINE transformation (to deal with % cover data). When I use a GLM I do not have any problem. But when I am trying to use a GAM model using mgcv package, to account for non-linearity I get an “error message”.
I use the following model: sp1.gam<-gam(asin(sqrt(0.01*SP1COVER))~ s(asin(sqrt(0.01*SP2COVER)))+ s(asin(sqrt(0.01*SP3COVER)))+ s(asin(sqrt(0.01*SP4COVER)))+ s(asin(sqrt(0.01*SP5COVER))), family=gaussian, data=plantcover, na.action=na.pass) The error message is the following: "Error in smooth.construct.tp.smooth.spec(object, data, knots) : A term has fewer unique covariate combinations than specified maximum degrees of freedom" It seems that some variables in the model give problems,…What is the reason of this error message? What I do is trying to erase randomly some of the variables (those that I expect to have more zeros) in the model (for instance run the same model without the SP5COVER term) and try if I get the error message again or not,… but this is time consuming. What can I do? Thanks! Francesc ______________________________________________ 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.
