[R] lme4 mcmcsamp matrix not PD

[Martin Henry H. Stevens]

Hi folks,
I am not providing a small replicable example, because I assume the  
problem is related to my quirky data (~650 obs.).
I am using the latest lme4, matrix and coda, and R 2.4.0.

I frequently get the following error message for this particular lmer  
model. I do not get this message for the vast majority of my uses of  
mcmcsamp.

I was wondering if it might be characteristic of particular kinds of  
problems.

 > modb <- lmer(log(basal+1) ~ nutrient*amd +  (1|rack) +  (1| 
gen:amd), data=dat.b2)

 > mod.mc <- mcmcsamp(modb, n=10^4)

Error: Matrix is not pd after safe_pd_matrix!
Error in t(.Call(mer_MCMCsamp, object, saveb, n, trans, verbose)) :
	error in evaluating the argument 'x' in selecting a method for  
function 't'

Cheers,
Hank

Dr. Hank Stevens, Assistant Professor
338 Pearson Hall
Botany Department
Miami University
Oxford, OH 45056

Office: (513) 529-4206
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http://www.cas.muohio.edu/~stevenmh/
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