Thanks for the help, Darren. Unfortunately, changing the F threshold did
not change anything. I see no reason why the origins of the images should
be a problem, and they appear to give perfectly reasonable (anatomically
correct) answers when treated as one entire group. I also avoided an
explicit mask in all the analyses.
Any other ideas?
-David
-----Original Message-----
From: Darren R. Gitelman [mailto:[log in to unmask]]
Sent: Saturday, September 30, 2000 3:04 PM
To: Kareken, David A.
Cc: [log in to unmask]
Subject: Re: 2-sample t-test
Dear David:
I think the message means that there ended up being no voxels whose
significance passed the Upper tail F probability threshold. (Assuming that
all con**.img images are appropriately oriented with the proper origins,
etc. Also make sure you haven't masked the images at the second stage of
the analysis. I suggest going into preferences and changing your F
threshold to 1 (= no threshold) and rerunning your stats.
HTH,
Darren
>SPMers,
> Can someone help with the following message? I have a two group PET
>activation study. I used a Condition x Subject model to generate con.img's
>for each subject to take to a second (RFX) level analysis. When I enter
>these two groups into this model, however, the analysis proceeds until the
>last image plane/plank, and produces the following error output.
>
> Warning: No inmask voxels - empty analysis!
> > In C:\Program Files\spm99\spm_spm.m at line 1074
> In C:\Program Files\spm99\spm_spm_ui.m at line 1427
> Design parameters : ...intrinsic
>autocorrelation ...V, & traces ...scaling DesMtx
>...closing image files ...smoothnessWarning: Divide by
zero.
> > In C:\Program Files\spm99\spm_spm.m at line 1137
> In C:\Program Files\spm99\spm_spm_ui.m at line 1427
> Warning: Divide by zero.
> > In C:\Program Files\spm99\spm_spm.m at line 1138
> In C:\Program Files\spm99\spm_spm_ui.m at line 1427
> ??? Index exceeds matrix dimensions.
>
> Error in ==> C:\Program Files\spm99\spm_spm.m
> On line 1142 ==> FWHM = FWHM*((RESEL/prod(FWHM(1:N))).^(1/N));
>
> Error in ==> C:\Program Files\spm99\spm_spm_ui.m
> On line 1427 ==> spm_spm(VY,xX,xM,F_iX0,xC,xsDes)
>
> By the first line, it appears to suggest that there are no voxels to
>analyze. I submitted each of the groups separately, as well as one entire
>group, to a one sample t-test to test the con.img's against a null
>hypothesis and it works fine, producing the expected results. Thus, there
>doesn't appear to be a particular problem with the images themselves.
>
> Suggestions?
>
>Thanks all.
>
>________________________________
>David A. Kareken, Ph.D., ABPP
>Assistant Professor & Director
>Neuropsychology Section, Department of Neurology
>RI 5999C
>Indiana University School of Medicine
>Indianapolis, IN 46202
>(317) 274-7327 (voice)
>(317) 274-1337 (fax)
-------------------------------------------------------------------------
Darren R. Gitelman, M.D.
Cognitive Neurology and Alzheimer's Disease Center
E-mail: [log in to unmask] WWW:
http://www.brain.northwestern.edu
Voice: (312) 908-9023 Fax: (312) 908-8789
Northwestern Univ., 320 E. Superior St., Searle 11-470, Chicago, IL 60611
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