Hi Francois
If you want to test the model with
three random effects including intercept, time, and time*time as the
random effects then you should use [1 2 3] (these are the columns
corresponding to those covariates in X). Actually, for the example in
the wiki page we first tested [1 2 3] but the model [1 2] was the
best at most vertices. In general, you need more than 4 repeated
measures to think of including three random effects in the model for
the covariance. Otherwise two random effects are usually enough (you
can still include time*time in the model for the mean as in the wiki
). Also, computation time increases quickly with the number of random
effects.
There is an oncoming paper that will
expand more on our longitudinal mass-univariate analyses with lme
(hopefully soon).
Best
-Jorge
>________________________________
> De: "Lalonde, Francois (NIH/NIMH) [E]" <flalo...@mail.nih.gov>
>Para: "freesurfer@nmr.mgh.harvard.edu" <freesurfer@nmr.mgh.harvard.edu>
>Enviado: Miércoles 27 de marzo de 2013 15:20
>Asunto: [Freesurfer] specifying random effects in LME (Linear Mixed Effects
>models)
>
>I am following the wiki page for LME analysis and I have a quick question.
>The Mass-univariate example near the bottom of the page proposes an initial
>model that contains intercept, linear and quadratic terms as random effects.
>However, the examples just below for lme_mass_fit_EM_init(),
>lme_mass_fit_EM_Rgw() only have [1 2] as selected random effects. Should the
>vector Zcols contain [1 2 3] as selected random effects in order to test the
>proposed model?
>
>Thanks,
>Francois
>
>François Lalonde, Ph.D.
>Child Psychiatry Branch
>NIMH / NIH
>10 Center Drive, Room 3N202
>Bethesda, MD 20892
>
>_______________________________________________
>Freesurfer mailing list
>Freesurfer@nmr.mgh.harvard.edu
>https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
>
>
>The information in this e-mail is intended only for the person to whom it is
>addressed. If you believe this e-mail was sent to you in error and the e-mail
>contains patient information, please contact the Partners Compliance HelpLine
>at
>http://www.partners.org/complianceline . If the e-mail was sent to you in error
>but does not contain patient information, please contact the sender and
>properly
>dispose of the e-mail.
>
>
>
>
_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
The information in this e-mail is intended only for the person to whom it is
addressed. If you believe this e-mail was sent to you in error and the e-mail
contains patient information, please contact the Partners Compliance HelpLine at
http://www.partners.org/complianceline . If the e-mail was sent to you in error
but does not contain patient information, please contact the sender and properly
dispose of the e-mail.
