Re: [R] A question on modeling brain growth using GAM

2017-04-07 Thread Leon Lee
Simon I wonder whether I can take advantage of this thread and ask you another related question. Now, I want to get the 95%CI of the fit and their derivatives as well. For the original fitted curves, It is straightforward as the option "type=terms" can be used to get the CI for the fixed effect. N

Re: [R] A question on modeling brain growth using GAM

2017-04-07 Thread Leon Lee
Hi, Simon Thank you for your explanation! I followed the instructions and successfully get the predicted values with both fixed and random effects incorporated: pred.new=predict.gam(gamm1$gam,newdata,type="response"). Also, what I meant to say was "plot(gamm1$gam, pages=1)" for left and right fig

Re: [R] A question on modeling brain growth using GAM

2017-04-06 Thread Simon Wood
> > gamObj=gam(brainVolume~ s(correctedAge) + s(subjIndexF, bs="re") + > s(subjIndexF, correctedAge, bs="re"), method="REML", data=mydata), > where subjIndexF is a factor for each subject. I was thrown an error > saying "more coefficients than data". > --- I'm not sure exactly how many scans a

Re: [R] A question on modeling brain growth using GAM

2017-04-06 Thread Simon Wood
If 'subjIndexF' is a factor for subject, then s(subjIndexF, bs="re") will produce a random effect for subject. i.e. each subject will be given its own random intercept term, which is a way that repeated measures data like this are often handled. The reason for the s(subjIndexF, bs="re") syntax

Re: [R] A question on modeling brain growth using GAM

2017-03-30 Thread David Winsemius
> On Mar 30, 2017, at 6:56 AM, Leon Lee wrote: > > David > > Thank you for your reply. I apologize if I posted in the wrong forum, as I > really couldn't decide which forum is the best place for my question and I > saw similar questions asked before in this forum. > > I agree that a sample

Re: [R] A question on modeling brain growth using GAM

2017-03-30 Thread Leon Lee
David Thank you for your reply. I apologize if I posted in the wrong forum, as I really couldn't decide which forum is the best place for my question and I saw similar questions asked before in this forum. I agree that a sample of ~30 subjects (70 scans in total), the model can be too complicated

Re: [R] A question on modeling brain growth using GAM

2017-03-28 Thread David Winsemius
> On Mar 28, 2017, at 9:32 AM, Leon Lee wrote: > > Hi, R experts > > I am new to R & GAM toolbox and would like to get inputs from you all on my > models. The question I have is as follows: > I have 30 subjects with each subject being scanned from one to three times > in the first year of life.