R Under development (unstable) (2025-07-22 r88445 ucrt) -- "Unsuffered Consequences"
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> library(parfm)
Loading required package: survival
Loading required package: optimx
> data(asthma)
> head(asthma)
  Patid Begin End Status Drug Fevent
1     1     0  15      1    0      1
2     1    22  90      1    0      0
3     1    96 325      1    0      0
4     1   329 332      1    0      0
5     1   338 369      1    0      0
6     1   370 412      1    0      0
> asthma <- asthma[asthma$Fevent==0,]
> 
> set.seed(1)
> data <- asthma[sample(1:nrow(asthma), 200),]
> 
> parfm(Surv(Begin, End, Status)~Drug, cluster="Patid", 
+       data=data, dist="weibull", frailty="gamma")

Frailty distribution: gamma 
Baseline hazard distribution: Weibull 
Loglikelihood: -906.338 

       ESTIMATE SE    p-val 
theta   0.000               
rho     0.754               
lambda  0.079               
Drug   -0.004   0.104 0.969 
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Kendall's Tau: 0 
Warning messages:
1: In parfm(Surv(Begin, End, Status) ~ Drug, cluster = "Patid", data = data,  :
  optimisation procedure did not converge,
              conv = : see ?optimx for details
2: In parfm(Surv(Begin, End, Status) ~ Drug, cluster = "Patid", data = data,  :
  negative variances have been replaced by NAs
 Please, try other initial values or another optimisation method
> 
> data$time <- data$End - data$Begin
> 
> parfm(Surv(time, Status)~Drug, cluster="Patid", data=data,
+       dist="weibull", frailty="gamma")

Frailty distribution: gamma 
Baseline hazard distribution: Weibull 
Loglikelihood: -897.482 

       ESTIMATE SE    p-val 
theta   0.289   0.157       
rho     0.901   0.073       
lambda  0.028   0.008       
Drug   -0.024   0.194 0.901 
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Kendall's Tau: 0.126 
> 
> proc.time()
   user  system elapsed 
  17.15    0.70   17.82