Hi Ged,
thank you a lot for your answer. I am afraid I know too little of SPM to 
actually follow you, but I have tried to do the tests you have suggested:

xX.xKXs.X, xX.X, SPM.xX.K, and SPM.xX.W are all complex.

xX.X seems to be fine, as far as I can tell.

SPM.xVi.V in turn is not complex.

Also pointing to your suspect of a bug in the rWLS toolbox, I have now 
found out that the "complex data" error only occurs when I choose 'WLS' 
as as (co-) variance structure for serial correlations and NOT when I 
choose 'AR(1)' or 'WLSAR'.
When I choose 'WLSAR' the contrast manager works fine. The only (small?) 
problem in this case is that I cannot use the RWLS/Plot residual 
timeseries anymore, and I obtain the error message:
"The specified SPM was not a wls or a wlsAR model'

Hopefully the RWLS toolbox authors are also tuned to the list!

Marco


Ged Ridgway wrote:
> Hi Marco,
> 
> I know nothing about the RWLS toolbox, but it does sound like it's a bug 
> there, rather than in the rest of SPM. Based on the comments in the 
> (standard, not RWLS) spm_spm.m,
>   xX.nKX - design matrix (xX.xKXs.X) scaled for display
> I can think of a couple of things to try:
> 
> Check whether xX.xKXs.X has complex elements, or whether the display 
> scaling is just messing things up -- I expect the former, unfortunately, 
> but if it turns out it is just the latter, then you could try loading 
> the SPM.mat after estimation, removing the complex values in xX.nKX and 
> then resaving; the results might then work alright, although you'd have 
> to ignore the displayed matrix.
> 
> If xX.xKXs.X is complex, double check that the original xX.X is what you 
> expect, and then investigate SPM.xX.K and SPM.xX.W, and if the latter is 
> complex, then also look at SPM.xVi.V. If that is where the problem 
> appears, then it sounds like ReML has gone awry, even if the estimation 
> appeared to go alright. I can't think of much to suggest then though, 
> other than contacting the RWLS toolbox authors...
> 
> Best,
> Ged
> 
> 
> marco tettamanti wrote:
>> Dear list,
>> I am encountering a problem with a first-level statistical analysis 
>> using the RobustWLS toolbox. The model estimation runs fine, I can 
>> also define a set of statistical contrasts via the command line (using 
>> MakeCon), but when I attempt to display the contrast effects clicking 
>> on the "Results" button, I get an "Image CDdata can not be complex" 
>> error (see error message attached below). Oddly, this only happens for 
>> a subset of subjects.
>> I have found a previous mailing-list thread on this subjects, 
>> including the following response:
>>
>> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0703&L=SPM&P=R10863&I=-3
>>
>> in which Ged Ridgway suggested to enter the following command in matlab:
>>
>> any(~isreal(SPM.xX.nKX));
>>
>> When I do this, I find that the nKX structure is indeed complex for 
>> the subjects in which I encounter the problem and that it is not 
>> complex for the "good" subjects.
>>
>> Concerning the RWLS toolbox, it doesn't make any difference whether I 
>> enter the unsmoothed data or not: the "good" subjects always run fine, 
>> whereas the "bad" subjects always give the "complex data" error. Also, 
>> rWLS convergence does not seem to be a problem.
>> However, an "equivalent" statistical model estimation in SPM5 (i.e. 
>> outside the RWLS toolbox) does not produce any "complex data" error, 
>> even in the bad subjects.
>>
>> The problem seems to be architecture and software independent: it 
>> occurs both on 32bit and 64bit linux, with several SPM5 revisions 
>> (826, 748, 665) and with two different matlab releases (2006a, 2007a)...
>>
>> Does anyone have an idea of what's going on?
>> Thank you so much,
>> Marco
>>
>>
>> SPM5: spm_results_ui (v$Rev: 816 $)                10:26:22 - 06/06/2007
>> ========================================================================
>> ??? Error using ==> image
>> Error using ==> image
>> Image CData can not be complex..
>>
>> Error in ==> spm_conman at 960
>>             hDesMtxIm = image((varargin{2}.nKX+1)*32);
>>
>> Error in ==> spm_conman at 929
>>             spm_conman('ImDesMtx',xX,H.hDesMtxAx) %-Depict DesMtx
>>
>> Error in ==> spm_conman at 812
>>     [F,cF] = 
>> spm_conman('Initialise','on',SPM,STATmode,n,Prompt,Mcstr,OK2chg);
>>
>> Error in ==> spm_getSPM at 278
>> [Ic,xCon] = spm_conman(SPM,'T&F',Inf,...
>>
>> Error in ==> spm_results_ui at 274
>>         [SPM,xSPM] = spm_getSPM;
>>
>> ??? Error using ==> [hReg,xSPM,SPM] = spm_results_ui;
>> Error using ==> image
>> Error using ==> image
>> Image CData can not be complex..
>>
>> ??? Error while evaluating uicontrol Callback
>>
>>
>>
> 

-- 
Marco Tettamanti, Ph.D.
San Raffaele Scientific Institute
Facoltà di Psicologia
Via Olgettina 58
I-20132 Milano, Italy
Tel. ++39-02-26434888
Fax ++39-02-26434892
Email: [log in to unmask]