[R] scatterplot smoothing using gam

[Tony Long]

All:

	I am trying to use gam in a scatterplot smoothing problem. 
The data being smoothed have greater 1000 observation and have 
multiple "humps".  I can smooth the data fine using a function 
something like:

out <- ksmooth(x,y,"normal",bandwidth=0.25)
plot(x,out$y,type="l")

The problem is when I try to fit the same data using gam

out <- predict.gam(gam(y~s(x)),se=TRUE)
plot(x,out$fit,type="l")

I only seem to get fits that would correspond to "big" bandwidths 
using ksmooth, and straight lines are always fit to the data.  I do 
not appear to appreciate how to "control bandwidth" using gam.  As 
even if I apply something like the gam model above to the smoothed 
"out$y" generated using ksmooth it tends to flatten out the smoothing 
curve.
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Tony Long

Ecology and Evolutionary Biology
Steinhaus Hall
University of California at Irvine
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email:  tdlong at uci.edu
http://hjmuller.bio.uci.edu/~labhome/