From: Loki Natarajan <loki_at_math.ucsd.edu>

Date: Wed 26 Jul 2006 - 08:52:01 EST

15: NaNs produced in: log(x)

16: NaNs produced in: log(x)

*>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Wed Jul 26 08:59:25 2006

Date: Wed 26 Jul 2006 - 08:52:01 EST

Hi,

I was very much hoping someone could help me with the following.
I am trying to convert some SAS NLMIXED code to NLME in R (v.2.1),
but I get an error message. Does anyone have any suggestions?
I think my error is with the random effect "u" which seems to be
parametrized differently in the SAS code. In case it's helpful,
what I am essentially trying to do is estimate parameters using ML in a
measurement error setting with some validation data (indicated by
vs.flag). Any help would be greatly appreciated.I apologize for the
clumsiness of the R code.

Many thanks in advance.

#################################################################SAS Code:

proc nlmixed data=repdat

parms b0 -3 b1 -.135 a0 3 a1 4 sigsq 0.25;

if vs.flag = 1 then do;

eta1 = b0 + b1*lnbldT;

llbin = anybc.cens.ind*eta1 - log(1+exp(eta1));
eta2 = a0 + a1*lnndsTs;

llnorm = -1/(2*sigsq)*(lnbldT - eta2)**2 - .5*log(sigsq);
ll = llbin + llnorm;

end;

else do;

eta2 = a0 + a1*lnndsTs;

eta1 = b0 + b1*eta2 + u;

llbin = anybc.cens.ind*eta1 - log(1+exp(eta1));
ll = llbin;

end;

sigma2 = sigmasq*b1**2 /*variance of random effect;
model anybc.cens.indic ~ general(ll);

random u ~ normal(0,sigma2) subject = CaseID; */;
run;

####################################################################R Code with error message:

me.km.nlme <- nlme(model = anybc.cens.indic ~
vs.flag*((anybc.cens.indic*(b0+b1*lnbldT) - log(1 + exp(b0+b1*lnbldT))) +
(((-1/(2*sigsq))*(lnbldT -a0 -a1*lnndsTs)^2) - 0.5*log(sigsq))) +
(1-vs.flag)*((anybc.cens.indic*(b0+b1*(a0 + a1*lnndsTs + u))) - log(1 +
exp(b0+b1*(a0 + a1*lnndsTs + u)))), fixed =
list(a0~1,a1~1,b0~1,b1~1,sigsq~1),na.action=na.omit, data=rc.df,
method="ML", random=u~1|CaseID,

start = c(a0=0, a1=1, b0=-3, b1 = -0.135, sigsq = 0.25))

+ Error: Singularity in backsolve at level 0, block 1
In addition: There were 16 warnings (use warnings() to see them)

*> >
**>
**> warnings()
*

Warning messages:

1: Singular precision matrix in level -1, block 5 2: Singular precision matrix in level -1, block 5 3: Singular precision matrix in level -1, block 5 4: NA/Inf replaced by maximum positive value 5: Singular precision matrix in level -1, block 5 6: Singular precision matrix in level -1, block 5 7: Singular precision matrix in level -1, block 5 8: NA/Inf replaced by maximum positive value 9: NaNs produced in: log(x) 10: NaNs produced in: log(x) 11: NaNs produced in: log(x) 12: NaNs produced in: log(x) 13: NaNs produced in: log(x) 14: NaNs produced in: log(x)

15: NaNs produced in: log(x)

16: NaNs produced in: log(x)

#####################################################################

phone: 858 822 4763 Fax: 858 822 6897 ______________________________________________R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Wed Jul 26 08:59:25 2006

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