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Dear Hweeling
Your code looks fine. Unfortunately, this error message just says something is unexpected about the DCMs, but doesn't provide detail. Please could you check that GCM is a cell array with one row per subject? And that when you type:

GCM{1}

And press enter into the Matlab workspace, you either see the filename of the DCM, or you see a series of fields. If you see a series of fields, please could you check this includes ones named 'F' and 'Ep'? If you see a filename, please could you load it in and type:

DCM

And press enter. And then check it has fields named 'F' and 'Ep'?

Best
Peter

-----Original Message-----
From: SPM (Statistical Parametric Mapping) <[log in to unmask]> On Behalf Of Hwee Ling Lee
Sent: 05 February 2019 09:20
To: [log in to unmask]
Subject: [SPM] error in PEB DCM

Dear all,

I have encountered an error on my DCM analyses, and I hope to get some guidance to resolve the issue. I'm currently using SPM version 7487.

I have 2 groups of participants, 56 in one group and 23 in another group. I have completed the creating the GCM variable using spm_dcm_bmr(GCM). I would like to compare group 1 vs. group 2 to examine connectivity differences between the 2 groups.

However, when I tried to use this code:

M = struct();
M.alpha = 1;
M.beta = 16;
M.hE = 0;
M.hC = 1/16;
M.Q = 'all';

M.X(:,1) = ones(79,1);
M.X(:,2) = [ones(56,1)*1; ones(23,1)*-1]; M.Xnames = {'Group mean', 'Group diff'};

field = {'A'};

PEB = spm_dcm_peb(GCM, M, field);
BMA = spm_dcm_peb_bmc(PEB(1));

I get an error message:

Undefined function or variable "pC".

Error in spm_find_pC (line 52)
if isstruct(pC)

Error in spm_dcm_peb (line 148)
    q = spm_find_pC(DCM,field);                 % parameter indices

Thanks!

Cheers,
Hweeling