Re: [Freesurfer] Interactions for continuous variables

From mri_glmflit --help :

--X design matrix file

Explicitly specify the design matrix. Can be in simple text or in matlab4 format. If matlab4, you can save a matrix with save('X.mat','X','-v4');

It does not need/expect any extension.

doug

Jerry Yeou-Wei Chen wrote:

Regarding custom design matrices, does the --X flag require a design matrix in matlab format? If so, can I simply create it in a text editor and name it with the suffix ".mat"? Also, if I use the --X to specify a design matrix, am I still supposed to specify the fsgd file? Thanks,

• Jerry

On Wed, Apr 9, 2008 at 4:58 PM, Jerry Yeou-Wei Chen <jyw.chen@utoronto.ca mailto:jyw.chen@utoronto.ca> wrote:

Great! Thanks!
- Jerry


On Wed, Apr 9, 2008 at 3:50 PM, Doug Greve
<greve@nmr.mgh.harvard.edu <mailto:greve@nmr.mgh.harvard.edu>> wrote:


    You can pass custom design and contrast matrices to
    mri_glmfit, so you can pass the same matrices to mri_glmfit
    that you would use with spm. Alternatively, you can set up an
    fsgd file with a 3rd continuous variable that is the produce
    of the first two.

    doug





    Jerry Yeou-Wei Chen wrote:

...

    Hello,
    I would like to know how to examine an interaction between
    continuous variables.
    In SPM, my understanding is that a new interaction regressor,
    comprised of the product of the two continuous variables of
    interest, can be coded and entered into the model.
    Would this be appropriate for CTA group analysis in
    FreeSurfer? Is there any difference if I use the old command
    line method or the QDEC GUI?
    Thanks,
    - Jerry

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