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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