gam
On 05/17/2012 06:17 PM, Mahnaz Rabbaniha wrote:
Dear all i have done GAM for data ( they are non- normal and i find regression between Sillaginidae with several hydrological factors),i done : [1] "depth" "temperature" "salinity" "Sillaginidae"
> pairs(sc,panel=function(x,y){points(x,y);lines(lowess(x,y))})
model<-gam(Sillaginidae~s(temperature)+s(salinity)+s(depth))
but i take this message: Error in smooth.construct.tp.smooth.spec(object, dk$data, dk$knots) : A term has fewer unique covariate combinations than specified maximum degrees of freedom please help me what can i do? or what is meaning this sentence?
It means that you don't have a lot of different values for one of your covariates. You can check which with length(unique(depth)) length(unique(temperature)) length(unique(salinity)) Unless you have a lot of data, that the sensible thing to is probably to fit a straight line rather than a smooth curve. The other thing to do is to define the maximum flexibility of the curve, e.g. model<-gam(Sillaginidae~s(temperature, k=6)+s(salinity)+s(depth)) I hope this helps. Bob
Bob O'Hara Biodiversity and Climate Research Centre Senckenberganlage 25 D-60325 Frankfurt am Main, Germany Tel: +49 69 798 40226 Mobile: +49 1515 888 5440 WWW: http://www.bik-f.de/root/index.php?page_id=219 Blog: http://blogs.nature.com/boboh Journal of Negative Results - EEB: www.jnr-eeb.org