Dear all,
I have encountered the following problem where coxme seems to allow
model with only random effect in R 2.11.1 but not in R 2.13.0. Following
is the error message using rat example data. Any comment on this is
appreciated.
In R2.13
> library(coxme)
> rat1 <- coxme(Surv(time, status) ~ rx + (1|litter), rats)
> rat0 <- coxme(Surv(time, status) ~ (1|litter), rats)
Error in coxme.fit(X, Y, strats, offset, init, control, weights =
weights, :
No starting estimate was successful
In R 2.11.1
> library(coxme)
> rat1 <- coxme(Surv(time, status) ~ rx + (1|litter), rats)
> rat0 <- coxme(Surv(time, status) ~ (1|litter), rats)
> rat0
Cox mixed-effects model fit by maximum likelihood
Data: rats
events, n = 40, 150
Iterations= 22 113
NULL Integrated Penalized
Log-likelihood -185.6556 -184.8205 -177.8707
Chisq df p AIC BIC
Integrated loglik 1.67 1.00 0.19623 -0.33 -2.02
Penalized loglik 15.57 12.03 0.21372 -8.50 -28.82
Model: Surv(time, status) ~ (1 | litter)
Random effects
Group Variable Std Dev Variance
litter Intercept 0.6441629 0.4149458
Ruby Chang
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