Kristine/Doug,

Are you missing Dependent Variable values or Independent Variable Values?

If you are missing some IV values, there are two potential solutions:
(1) Drop the subject;
(2) Impute the value of that subject given other variables and relationships of those variables and the variable with the missing value.

If you are missing some DV values, the easiest solution would be to use GLM_Flex (http://nmr.mgh.harvard.edu/harvardagingbrain/People/AaronSchultz/GLM_Flex.html).

The one caveat of GLM_Flex is that we don't have a computation for surface smoothness yet, we should probably talk to Doug about the best way to deal with this issue. Another caveat is that it won't be useable in some of the freesurfer viewing tools (such as qdec as the file structure of the model is different), but contrasts can be viewed with tksurfer.

One other caveat, the output of GLM_Flex is T/F-statistics, not log-transformed p-values as is traditionally done in Freesurfer. I think that this will be updated at some point in the future.

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Fri, Feb 24, 2012 at 3:27 PM, Kristine Beate Walhovd <k.b.walhovd@psykologi.uio.no> wrote:

Hi,

we´re running FS 5.1 and have a data set with a lot of missing values.
There are different subsets of persons missing different values of
interest, and we´re running analyses on concat files. mri_glmfit not
qdec). Is there anyway we can run analyses w/ missings in the fsgd file?

Best,

Kristine

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