Dear R-help,

I am using R 2.14.1 on Windows 7 with the 'gfcure' package (cure rate model).
I have included the treatment variable in the cure part of the model as shown below:


Ų  ref_treat <- gfcure(Surv(rem.Remtime,rem.Rcens)~1,~1+strata(drpa)+factor(treat(delcure)),data=delcure,dist="loglogistic")

>From that I can obtain the coefficients, standard errors etc as per alternative models (with covariates only fitted to the survival part of the model say).

> summary(ref_treat)

However, only one standard error is output:

Log-logistic mixture model

The maximum loglikelihood is -927.0449

Terms in the accelerated failure time model:
            Coefficients  Std.err  z-score   p-value
Log(scale)     -0.894528   0.0236 -37.8324 0.0000000
(Intercept)     6.929351   0.0151 460.4157 0.0000000

Terms in the logistic model:
                        Coefficients  Std.err  z-score   p-value
(Intercept)                 2.542726
strata(drpa)drpa=2         18.767777
factor(treat(delcure))2     0.184192
factor(treat(delcure))3     0.472809
factor(treat(delcure))4     0.255565 953.6876   0.0003 0.9997862
factor(treat(delcure))5     0.401713
Warning message:
In sqrt(diag(solve(object$infomat))) : NaNs produced


Can anyone explain why this is the case?

Very many thanks,
Laura

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