[R-sig-ME] Cholmod warning with glmer

[leanne heisler]

Thank you Dr. Winsemius, when I converted the LONG values to positives the first error does not occur ( Error in mer_finalize(ans) : Downdated X'X is not positive definite, 1.). Would you be able to explain why this is, just curious!
 
LONG is actually the longitude at which samples were collected.
> table(data$LONG)
100 101 102 103 104 105 106 107 108 109 110 111 112 113 
2 9 3 1 106 304 40 5 69 78 114 122 106 7 
NG is a proportion between 0 and 1
> table(data$NG)
 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22 0.23 
94 27 35 33 28 22 60 23 14 7 6 13 10 14 1 3 3 4 4 7 5 3 19 7 
0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.4 0.41 0.42 0.43 0.44 0.45 0.46 0.47 
4 4 3 11 5 8 7 10 8 8 11 4 6 7 8 12 17 7 6 8 7 10 10 6 
0.48 0.49 0.5 0.51 0.52 0.53 0.54 0.55 0.56 0.57 0.58 0.59 0.6 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.7 0.71 
12 18 15 8 4 6 19 5 7 7 2 7 5 4 5 2 3 4 3 9 1 7 15 7 
0.72 0.73 0.74 0.75 0.76 0.77 0.78 0.79 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 
6 4 2 1 6 3 6 1 5 7 9 4 7 7 2 5 2 6 13 7 2 8 7 6 
0.96 0.97 0.98 0.99 1 
7 9 6 13 1 
However, the last two warnings remain:
 
> dm=glmer(DM~PREC+(1|NEST)+(1|NG)+(1|LONG),data=data,family=poisson,REML=FALSE)
Warning messages:
1: In mer_finalize(ans) :
 Cholmod warning 'not positive definite' at file:../Cholesky/t_cholmod_rowfac.c, line 432
2: In mer_finalize(ans) :
 Cholmod warning 'not positive definite' at file:../Cholesky/t_cholmod_rowfac.c, line 432
3: In mer_finalize(ans) : singular convergence (7)
 
I've tried removing each random effect, and it works (with false convergence though) when LONG is removed (code below), so I think the problem lies with this random effect. If anyone has any suggestions as to why this variable is problematic in my model, it would be greatly appreciated!
 
> dm=glmer(DM~PREC+(1|NEST)+(1|NG),data=data,family=poisson,REML=FALSE,verbose=TRUE)
 0: 6240.2919: 1.34570 0.528027 3.19617 -0.00146991
 1: 6240.1850: 1.34569 0.528031 3.19616 -0.00156918
 2: 6240.1850: 1.34569 0.528031 3.19616 -0.00156918
Warning message:
In mer_finalize(ans) : false convergence (8)
 
Thank you,
 Leanne Heisler
 Graduate Student
 Department of Biology
 University of Regina