Rik,
Thanks for this. Unfortunately, this solution didn't work. When I tried to
test the sum of pairwise differences between components as suggested below,
the contrast manager accepted the specification but then crashed out with
the error message "matrix dimensions must agree" when I clicked OK. I tried
it again after running the analysis without the realignment parameters as
covariates, and got the same error message. However, this seemed to work:
exp con
1 0 0 ... -1 0 0 ...
0 0 1 ... 0 0 -1 ...
Also, I assume that if I did get the result I wanted from this comparison I
would have to plot the fitted responses to see what direction the
differences were in? FYI, I modelled the responses using only the first
order fourier component with the window length set to the image acquisition
time.
thanks,
Greig
> From: Rik Henson <[log in to unmask]>
> Reply-To: Rik Henson <[log in to unmask]>
> Date: Thu, 05 Oct 2000 08:46:07 +0100
> To: Greig de Zubicaray <[log in to unmask]>
> Cc: "[log in to unmask]" <[log in to unmask]>
> Subject: Re: fourier sets and F-contrasts
>
>
> Greig
>
> Simply construct an F-contrast comparing each Fourier component
> separately, eg:
>
> exp con
>
> 1 0 0 ... -1 0 0 ...
> 0 1 0 ... 0 -1 0 ...
> 0 0 1 ... 0 0 -1 ...
>
> or more simply, with N Fourier components, type:
>
> eye(N) -eye(N)
>
>
> Rik
>
>
>
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> DR R HENSON
> Institute of Cognitive Neuroscience &
> Wellcome Department of Cognitive Neurology
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