Dear DCMers,
there's been already some discussion about the following problem:
When performing DCM model estimation (DCM10), mostly during the first iterations the following error / warning occurs:
"Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = -1.0000000000e+00"
However, the estimation seems to continue properly with final convergence.
Back in 2005, it was suggested:
"... this points to problems with matrix inversion during the M-step - we
have seen that a few times in the past. Karl has very recently
updated the parameter estimation scheme (spm_nlsi_GN) to overcome
this problem. If you use the most recent version of this routine, it
should no longer occur. I am not sure whether this version is in the
updates directory yet; I will check this with John.
If the same problem still occurs with the new code, please send me
your model and we will have a look at it.
All the best,
Klaas..."
However, in most models this problem still occurs 2-3 times in the beginning though having the recent SPM/DCM installed. Can I trust the models estimated? Is there a fixed version of spm_nlsi_GN out there.
I am looking forward to your suggestions.
Best wishes,
Robert
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