Tom,
thanks a lot for taking a look at this issue. I'll make the change the code
that you have suggested and try it out.
All the best,
Jan
Thomas Nichols wrote:
> Jan,
>
> Reviewing the messages Satoru referenced and the code (spm_getSPM.m and
> spm_list's calls to spm_P) there's no reason that the extent threshold
> question should be omitted in the case of conjunctions. In particular,
> in the case of the inference on the 'Conjunction Null' the theoretical
> result *is* available, and is just the usual result for a single image.
> (To see this, realize that inference under the conjunction null takes
> place with worst case scenerio possible, where one image is totally
> null, and all other images conjoined are completely and wildly
> significant, e.g. T>100 everywhere; in this worst case the null cluster
> sizes in the conjoined image will be exactly those in the single null
> statistic image.)
>
> Further, the exent threshold is of course just an arbitrary cut off, and
> even if applied, doesn't change cluster P-values. Lastly, when doing a
> global or partial null conjunction test, the cluster P-values are not
> available and will simply result in NaN's in the tabular output.
>
> So feel free to find the lines in spm_getSPM.m
> %-Extent threshold (disallowed for conjunctions)
> %-----------------------------------------------------------------------
> if ~isempty(XYZ) & nc == 1
> and remove the last bit, as in
> if ~isempty(XYZ)
>
> Let me know if this works OK for you. If so I'll add it to main code.
>
> -Tom
>
>
> On Tue, Sep 9, 2008 at 10:04 PM, Jan Gläscher <[log in to unmask]
> <mailto:[log in to unmask]>> wrote:
>
> Dear SPMers,
>
> just a quick question: is there a theoretical reason of why one cannot
> select an extent threshold for a conjunction or this just some ancient
> restriction that can discarded?
>
> Thanks,
> Jan
>
>
> --
> Jan Gläscher, Ph.D. Div. Humanities & Social Sciences
> +1 (626) 395-3898 (office) Caltech, Broad Center, M/C 114-96
> +1 (626) 395-2000 (fax) 1200 E. California Blvd
> [log in to unmask] <mailto:[log in to unmask]>
> Pasadena, CA 91125
>
>
>
>
> --
> ____________________________________________
> Thomas Nichols, PhD
> Director, Modelling & Genetics
> GlaxoSmithKline Clinical Imaging Centre
>
> Senior Research Fellow
> Oxford University FMRIB Centre
--
Jan Gläscher, Ph.D. Div. Humanities & Social Sciences
+1 (626) 395-3898 (office) Caltech, Broad Center, M/C 114-96
+1 (626) 395-2000 (fax) 1200 E. California Blvd
[log in to unmask] Pasadena, CA 91125
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