Dear Sir/Madam , I need to use " Gamma Frailty Model " in a simulation study ,so I should replicate the program many times and get estimates of " THETA and its Variance " or "Variance-Covariance" matrix Or Variace of random effect in Gamma frailty model in Survival analysis at each time of replication. But when I use " $frail " and " $Var " and "$THETA " to retrieve the estimate of THETA and its Variance for each replicate , I get NULL response and when I use " $coef " I retrieve the coeficients only but not THETA and its Variance. Since I need to get THETA and its Variance at each time of replication so I need to know the name of these variables as used in the source program . I would be very grateful if you could kindly guide and help me to use appropriate statment to get the name of required varibles used in the source program or if you could introduce me to anybody that could help me . Thanks a lot in advance . With The Best Regards , Mehdi Rahgozar