Dear SPM-Experts,
in a 2nd level ANOVA using the flexible factorial design option, I would
like to include covariates. SPM seems to re-order the values of the
covariates in a strange way.
The design looks like:
17 subjects, 16 first-level-con images from every subjects, representing
the levels of a 4x4 factorial design. I enter the main effect for factor
'subject' an the interaction of the other two factors into the design
matrix. I want to include subject age as a covariate, so I enter the
numbers:
23 27 33 27 27 42 28 27 23 32 28 24
34 44 18 43 26 .... (repeated 16 times)
After I run the design specification, SPM seems to have reordered the
values. In SPM.xC.rc I find the values:
>> SPM.xC.rc(1:17)'
ans =
23 26 43 18 44 34 24 28 32 23 27
28 42 27 27 33 27
This looks like the first value followed by the other numbers in
reversed order. I tried to include and exclude factors, using other
designs with fewer factor levels, nothing helped. I am using SPM5 with
MatlabR2006b, but also with MatlabR2009b and/or SPM8 I get the same result.
Am I doing something wrong here?
Best,
Thomas
--
Dr. Thomas Stephan
Arbeitsgruppe fuer funktionelle, strukturelle und molekulare Bildgebung
Zentrum fuer Sensomotorik
Klinikum Grosshadern der Universitaet Muenchen
Marchioninistr. 23
81377 Muenchen
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