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
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