[R] multiple comparisons for GAMs

Bird_Girl sonyarichmond at hotmail.com
Thu Aug 2 21:09:46 CEST 2012


Hi,

I have a question regarding whether it is possible to do post hoc tests on a
model fit with GAM {mgcv}.  My response variable is abundance (no.
individuals per plot), and I have one continuous predictor (light) and one
factor (height) which includes 7 levels. 

> mod2=gam(log_abundance~s(light)+height+te(light,by=height)+s(long)+s(lat))

The relationship between log_abundance and light at the seven levels of
height all differ significantly from the overall relationship between
log_abundance and light, and relationships at most of the 7 levels are not
linear.  I would like to do some kind of multiple comparison or post hoc
test to determine whether the relationship between log_abundance and light
differs significantly among the different levels of height (i.e., is the
relationship at 200 m different from that at 400 m)? Is there any way to do
this?

Thanks in advance, and I apologize if this is a stupid question – I am new
to R.




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