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Hi,

I'm doing group analysis using a slightly modified version of AA-mod v4.0b Matlab script to do a t-test of contrasts in SPM8. I'm getting the following error:

***** error: *******

SPM8: spm_spm (v4191)                  
========================================================================
Initialising parameters                 :                        ...done
Output images                           :                 ...initialised
Plane  46/46 , block   1/1              :                        ...done
Spatial non-sphericity (over scans)     :  ...writing resels/voxel image??? NaN's cannot be converted to logicals.

Error in ==> spm_est_smoothness at 260
FWHM(~FWHM) = 1;

Error in ==> spm_spm at 928
    [FWHM,VRpv,R] = spm_est_smoothness(VResI,VM,[nScan erdf]);

***** end error *******

With error debugging on, I see that V, Ix, Iy, Iz are non-empty, but FWHM = [NaN NaN NaN], and in fact d,dx,dy,dz are filled with NaN's when returned by the spm_sample_vol call in spm_est_smoothness:

[d,dx,dy,dz] = spm_sample_vol(V(i),Ix,Iy,Iz,1);


Thanks in advance for any pointers!
g