Hello Joerg,
It's hard to say without seeing the full design, but it may be the extra confound EVs are removing the mean difference between the two groups you want to study. In general the situations that generate the "integral steps" error message will not generate any significant results, but you can approximate these by running with a method ( e.g. -c -C ).
Kind Regards
Matthew
> Dear Mark,
>
> your suggestion sounds very convincing. I got it partly working but I'm running into a problem.
>
> If I run randomise with 8 EVs (design1.mat and design1.con shown below), I get a warning:
>
> $ randomise -i all_FA_skeletonised -o tbss -m mean_FA_skeleton_mask -d design_test3.mat -t design_test3.con -n 500 --T2 -V
> Loading Data:
> Data loaded
> 2.32228e+12 permutations required for exhaustive test of t-test 1
> Doing 500 random permutations
> Starting permutation 1 (Unpermuted data)
> Starting permutation 2
> Warning: tfce has detected a large number of integral steps. This operation may require a great deal of time to complete.
>
> Citing Matthew Webster: "This error usually means that the contrast isn't suitable for TFCE" (see https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=fsl;cafb18bc.1206), but what exactly does "not suitable" mean?
>
> The strange thing is that if I reduce the number of EVs from 8 to 5 (see design2.mat and design2.con) everything seems to work.
>
> Any thoughts on this?
>
>
> Thanks,
> Jörg
>
>
>
> ------ design1.mat ------
> /NumWaves 8
> /NumPoints 35
> /PPheights 1 1 1 1 1 1 1 1
> /Matrix
> 0 0 1 0 0 0 1 0
> 1 0 0 0 0 1 0 0
> 0 0 1 0 0 0 0 1
> ...
> ... [a total of 35 rows]
> ...
> ----------------------------
>
> ------ design1.con ------
> /ContrastName1 "subgroup1 > subgroup2"
> /NumWaves 8
> /NumContrasts 1
> /PPheights 1
> /RequiredEffect 1
> /Matrix
> 1 -1 0 0 0 0 0 0
> --------------------------------
>
> ------ design2.mat ------
> /NumWaves 5
> /NumPoints 35
> /PPheights 1 1 1 1 1
> /Matrix
> 0 0 1 0 0
> 1 0 0 0 0
> 0 0 1 0 0
> ...
> ... [a total of 35 rows]
> ...
> ----------------------------
>
> ------ design2.con ------
> /ContrastName1 "subgroup1 > subgroup2"
> /NumWaves 5
> /NumContrasts 1
> /PPheights 1
> /RequiredEffect 1
> /Matrix
> 1 -1 0 0 0
> --------------------------------
>
|