Hi, this scenario is fairly straightforward. You want to tell
randomise to demean the data (as you're not interested in the mean
here) with the -D option.
You then want to setup a single-EV design.mat model, where the scores
are the log(age) values for the subjects, but where you have also
subtracted the mean (across all subjects) of these log(age) scores -
i.e. the EV ends up having zero mean.
Your contrast is then a single [1].
Hope this helps? Cheers.
On 28 Mar 2007, at 19:32, Robert Terwilliger wrote:
> Dear FSL TBSS people,
>
> I searched and found a post within the archives
> regarding designing a "within-group" analysis in TBSS,
> where members within the group exhibit different
> levels of a specific condition. Despite this, I have
> not been able to design such a matrix/contrast set for
> my own group of subjects.
>
> I have tried using the Glm_gui (Mac) to set up such a
> design for use in randomise. I have also followed
> several examples from the Feat2 Practicals from the
> lectures to glean how to port that design to tbss.
> However, I remain empty-handed, mostly due to lack of
> experience with the interface.
>
> **************************************
>
> Here is a subset of my subjects from which, if you
> could provide an example design.mat/con file set, I
> could generalize to my larger pool of subejcts:
>
> two 10-yr old Females
> three 14-yr old Females
> two 16-yr old Females
>
> So, seven subjects in all.
>
> What would be the design.mat/.con if I would like to
> measure how FA is related to the natural log of the
> subjects' ages (on a voxel-wise basis).
>
> Any help is appreciated.
>
> Regards,
>
> Robert Terwilliger
> University of Pittsburgh
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
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