
Hi,
I've been using gamm4 to build GAMMs for exploring environmental influences on genetic ancestry.  Things have gone well and I have 2 very straightforward questions:
1. I've used method=REML.  Am I correct that this is an alternative method for estimating the smooth functions in GAMMs rather than GCV that is often used for GAMs?  I've read up on REML and it makes sense, but I'm confused about whether GCV is used for any part of the model formation of a GAMM with method=REML.  I think it is not.  Is this why no GCV score is returned for GAMMs through mgcv and gamm4?  For Gams I've always used the GCV scores to help with model selection, but I assume these aren't available for GAMMs estimated with REML.
2. Instead I've been using AIC values with GAMMs.  Is it correct to use the AIC value from the underlying linear mixed model, i.e. extracted using summary(gamm1$mer)?  Or is there another AIC calculated specifically for the gam object?
Many thanks for help with these (admittedly simple and boring) questions, I really like the mgcv and gamm4 packages which I've found very user friendly in conjunction with Wood (2006).
John 		 	   		  
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