Hi Russell,
Tom and Steve would have a better clue than me on this one, but I would say that your design.mat should represent both controls and patients in EV1 (demeaned), then age demeaned as EV2, then age of controls demeaned by the mean age of controls *only* (padded with 0 for patients) as EV3, age of patients demeaned by the mean age of patients *only* (padded with 0 for patients) as EV4.
Then your command should be:
randomise -i all_FA_skeletonised -o tbss -m mean_FA_skeleton_mask -d design.mat -t design.con -n 500 -c 3 -D -V
Now in your design.con: do you want to regress out the linear effect of age and age*group from your analysis or are you looking specifically at these effects?
In the first case, your contrast should be:
1 0 0 0
and/or -1 0 0 0
and in the second case:
0 1 0 0 (linear effect of age)
and/or 0 -1 0 0
0 0 1 -1 (interaction between age and group)
and/or 0 0 -1 1
Hope this helps,
Gwenaelle
> De: Russell Chu <[log in to unmask]>
> Objet: [FSL] age and age*group interaction for randomise and tbss
> À: [log in to unmask]
> Date: Jeudi 17 Juillet 2008, 5h20
> Hi,
> I processed some patients and controls with TBSS and am now
> trying to find
> the age effect and age*group interaction in randomise.
> Would someone please
> check my design and contrast matrices below? Also, in the
> design matrix, I
> subtracted the mean age from each individual subject's
> age; is this the
> proper way to demean the ages?
>
> Design matrix:
> EV1(control) EV2(patient) EV3(age) EV4(age*control)
> EV5(age*patient)
> 1 0 4 4 0
> 1 0 -4 -4 0
> 0 1 -9.8 0 -9.8
> ...
> ...
> 0 1 -1.2 0 -1.2
> 0 1 -3 0 -3
> 1 0 -4 -4 0
> 1 0 4.3 4.3 0
>
> Contrast matrix:
> EV1(control) EV2(patient) EV3(age) EV4(age*control)
> EV5(age*patient)
> control>meth 1 -1 0 0 0
> meth>control -1 1 0 0 0
>
> randomise -i all_FA_skeletonised -o tbss -m
> mean_FA_skeleton_mask -d
> design.mat -t design.con -n 100 -c 3 -V
>
> Also, after all permutations (only 100 for quick initial
> results) are
> finished, the following error occurs:
>
> terminate called after throwing an instance of
> 'NEWMAT::ConvergenceException'
> Aborted
>
> Any input on these issues would be greatly appreciated.
>
> Thanks,
> Russell
_____________________________________________________________________________
Envoyez avec Yahoo! Mail. Une boite mail plus intelligente http://mail.yahoo.fr
|