you have a couple options:
1) assuming you are using 64b linux, you can download a new version of qdec which supports selecting 'nuisance' variables in the design. you can get it here: http://surfer.nmr.mgh.harvard.edu/pub/dist/freesurfer/misc/linux-centos4_x86... copy qdec.bin to your $FREESURFER_HOME/bin/ dir. it will use your existing mri_glmfit to do the analysis, so its ok to overwrite the existing qdec.bin. let me know if you need it for another distribution.
or
2) dont use qdec, and create fsgd files instead (aka the command line option). some examples are found here:
https://surfer.nmr.mgh.harvard.edu/fswiki/FsgdExamples
n.
On Wed, 2010-03-17 at 11:34 -0700, Laluz, Victor wrote:
Hello Freesurfer folks,
I hope this question is simple to answer: Is there any way to do a surface-based group analysis, a-la qdec, without the limitation of 2 continuous variables?
My goal is to analyze a thickness relationship with continuous variable X, which I have so far analyzed controlling for variable Y. However, I ALSO want to control for variable Z. As it is in qdec, it forces me to select only 2 of either X Y and Z.
I have tried converting one of the variables to a discrete factor, but the results do not look the same at all.
Any advice you can give will be very appreciated; and, as we are currently working under a deadline of sorts, the sooner someone might get back to me the better... as always, I really appreciate the help.
Victor Laluz : Imaging Coordinator : UCSF Memory and Aging Center 415-476-1680 : 415-476-1816 (fax)