Hi,
 
I am hoping some one can help with this.
 
I am using nlme to fit a random coefficients model. It ran for hours before returning 
 
Error: Singularity in backsolve at level 0, block 1

The model is 
> plavix.nlme<-nlme(PLX_NRX~loglike(PLX_NRX,PD4_42D,GAT_34D,VIS_42D,MSL_42D,SPE_ROL,XM2_DUM,THX_DUM,b0,b1,b2,b3,b4,b5,b6,b7,alpha),
+ data=data,
+ fixed=list(b0 + b1+b2+b3+b4+b5+b6+b7+alpha~1),
+ random=b0+b1+b2+b3+b4+b5+b6+b7~1|menum,
+ 
+ start=c(b0=0,b1=0,b2=0,b3=0,b4=0,b5=0,b6=0,b7=0,alpha=5)
+ )

Can anyone tell me what this error means and how I can run the model?
 
Thanks,
 
Elizabeth Lawson

		
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