Hi Bronwyn, I think years-between-scans should be years-from-baseline-scans . You may need to compute that if what you have is really years between neighbouring scans.
1. Usually people use intercept and maybe years-from-baseline as random effects. I would not include too many random effects, as it each adds a lot of free parameters and you need a lot of data to fit all that in a meaningful way. Which of your columns are random effects can be passed lme_fit_FS(X,[1 2],Y(:,1)+Y(:,2),ni); for example has column 1 and 2 as random effects. 2. You can do a model comparison as described on our wiki https://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels <https://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels> You run the more complex model first (do the EM init and maybe RgGrow and RgW fit) and then the simple one (only the EMinit and RgW fit) and do a likelihodd ratio test. An example is on the above wiki. Best ,Martin > On 27 Feb 2017, at 04:16, Bronwyn Overs <b.ov...@neura.edu.au> wrote: > > Dear mailing list, > > I am trying to run a LME model using the matlab tools, but I’m unsure how to > specify the model we wish to run. We have a qdec file that contains the > following columns: > fsid, fsid-abse, years between scans, age at baseline, gender, group > > We want to specify a model where we can examine four interaction terms > (years*age, years*group, age*group, years*age*group), as well as random > effects for the intercept, years and age. My questions are: > 1. How do we specify a model that will include the random effects we want? > 2. How do we compare our full model (3 random effects) with a model excluding > the random effect for age? > > Kind regards, > Bronwyn Overs > Research Assistant > > Neuroscience Research Australia > Margarete Ainsworth Building > Barker Street Randwick Sydney NSW 2031 Australia > M 0411 308 769 T +61 2 9399 1883 F +61 2 9399 1265 > > neura.edu.au <http://neura.edu.au/> > <https://twitter.com/neuraustralia> > <https://www.facebook.com/NeuroscienceResearchAustralia> > <http://www.neura.edu.au/help-research/subscribe> > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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