Hi Livia,
the Paired Analysis wiki page that you cite, contains the steps to
create the differences and then run a glm analysis on the difference
files. In your case you would to the first steps exactly as on the wiki
and then you can create a more complex Second FSGD File with more than
one group. For that take a look at the glm tutorial where we have plenty
more examples for GLM.
If the time delta between the two time points differes a lot across
subjects, you may want to switch to linear mixed effects modeling. Also
if you have cases that dropped out (only one time point) or cases with
more than 2, mixed effects models will be the better choice. We have
matlab code for that (see also the wiki).
Best, Martin
On 05/03/2017 04:53 PM, Livia Liu wrote:
Dear FS experts，
I have two group and two times to do longitudinal cross analysis.
I looked your answer in
https://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg45870.html
and
https://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg52032.html
Sorry, I can’t understand what you said” you can either subtract the
two time points and then do a regular group analysis”
"subtract tp1 from tp2 manually and pass the result to mri_glmfit."
How to subtract the two time manually and how to do then ? Would you
please tell me more details?
And in my analysis, if I use the paired analysis, how to design
paired.fsgd and paired-diff.fsgd?
In http://surfer.nmr.mgh.harvard.edu/fswiki/PairedAnalysis I am sorry
to only see how to do in one group.
Looking forward to reply, and thanks very much.
Kind regards,
Livia
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