Dear Stephan:
The file in the Y.mad file is compressed so there is no way to use
uncompressed data with the typical Y.mad file. However, I wonder if hacking
spm_spm.m might do what you want. You possible could change these lines
839 spm_append(Y,'Y.mad',2)
change to spm_append(Y,'Y.mad',64)
and
855 spm_append(Y(:,tmp),'Y.mad',2);
change to spm_append(Y(:,tmp),'Y.mad',64);
This would result in saving the Y.mad data as doubles instead of as uint8.
I think the data then would be essentially raw, but John can comment
further. Of course the size of the Y.mad files would be 8 times bigger. The
Y.mad file does have a header which specifies the type of data so I'm
guessing if Russ' toolbox routines read these files correctly they should
be aware of the change in datatype, although I have not verified this.
Darren
At 03:36 PM 10/11/2002 -0400, you wrote:
>I'm using Russ Poldrack's SPM ROI Toolbox to extract mean % signal
>changes from an ROI, and would like to use the maximal % change for each
>subject in a mixed-effects analysis (t-tests in SPSS, etc.). However,
>I've read dire warnings that the compression of the Y.mad file would
>cause errors in the resulting stats, ruling out this analysis.
>
>Is there a way to modify SPM to get it to use uncompressed data in the
>Y.mad file? I suspect it is more complicated than simply changing the
>data type and removing the rounding routines in spm_append.m.
>Alternately, perhaps the ROI toolbox routines could be modified to read
>from the images directly?
>
>thanks,
>Stephan Hamann
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Darren R. Gitelman, M.D.
Cognitive Neurology and Alzheimer¹s Disease Center
E-mail: [log in to unmask]
WWW: http://www.brain.northwestern.edu
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Northwestern Univ., 320 E. Superior St., Searle 11-470, Chicago, IL 60611
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