[R] glmmPQL / "system is computationally singular"

[Spencer Graves]

	  Did you try "traceback()"?  What do you get?

	  I've had good luck with problems like this in listing the function 
then using "debug" to review while I walk throught the code line by line.

	  This may not be the issue here, but with "family=binomial", if the 
model being fit can achieve perfect separation, software of this type 
might generate error messages similar to what you describe.

	  hope this helps.
	  spencer graves

David Reitter wrote:

> Hi,
> 
> I'm having trouble with glmmPQL from the MASS package.
> I'm trying to fit a model with a binary response variable, two fixed  
> and two random variables (nested), with a sample of about 200,000  
> data points.
> 
> Unfortunately, I'm getting an error message that is difficult to  
> understand without knowing the internals of the glmmPQL function.
> 
> 
>>model <-  glmmPQL(primed ~ log(dist) * role , random = ~ dist |  
>>target.utt / prime.utt , family=binomial(link = "logit"),  
>>data=data.utts, niter=5, verbose = TRUE)
>>Loading required package: nlme
>>iteration 1
>>iteration 2
>>iteration 3
>>Error in solve.default(pdMatrix(a, fact = TRUE)) :
>>        system is computationally singular: reciprocal condition  
>>number = 8.65949e-32
>>In addition: Warning messages:
>>1: Singular precision matrix in level -1, block 4
>>2: Singular precision matrix in level -1, block 4
>>3: Singular precision matrix in level -1, block 4
>>4: Singular precision matrix in level -1, block 4
>>5: Singular precision matrix in level -1, block 4
> 
> 
> Any suggestions? Will a larger dataset (possible) solve the problem?
> 
> Thanks
> David
> 
> --
> David Reitter - ICCS/HCRC, Informatics, University of Edinburgh
> Blog: http://www.davids-world.com   Homepage: http://www.david- 
> reitter.com
> 
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