Dear Rik,
thanks for your note. Given a previously specified design matrix, how do
I run the equation for calculating the efficiency? I tried to review and
to explore a previous design, but of course, c was not specified.
??? Undefined function or variable 'c'.
How do I get c, and given that - how can I check out different
contrasts?
TIA- andreas
Rik Henson wrote:
>
> Lila -
>
> > Does SPM99 have a sequence optimization routine for event-related fMRI
> > studies similar to OptSeq?
>
> Not as comprehensive as OptSeq, no.
>
> However, you can create a design matrix in SPM (e.g., by
> answering "yes" to the "Stochastic Design?" option), and
> then use the equation:
>
> trace(c'*inv(xX.X(:,1:2)'*xX.X(:,1:2))*c)^-1
>
> (typed in the matlab window), details of which, see:
>
> http://www.mailbase.ac.uk/lists/spm/2000-06/0000.html
>
> http://www.mailbase.ac.uk/lists/spm/1999-07/0018.html
>
> Beware though of iterative optimisation of designs in this
> manner, if you want to preserve randomness from the
> subject's perspective (eg you may tend towards a blocked
> design).
>
> Rik
>
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