#  R code to enter data on times to   
#  reccurance of infections in kidney
#  dialysis patients
 

data set1;
 infile "c:\stat565\data\kidney_infection.txt";
 input ID age sex gn an pkd time status recur;
 age10=age-10;
run;

proc print data=set1; run;

# Enter the data into a data frame.

set1 <- read.table("c:/stat565/data/kidney_infection.txt",
      header=F, col.names=c("id", "age", "sex", "gn", "an", "pkd", "time", "status", "recur")) 
      set1$age10 <- set1$age-10

set1

fitm <- coxph(Surv(time, status) ~ age10 + sex + gn + an + pkd
                + cluster(id), data = set1, robust=T, method="efron")
summary(fitm)


# Fit a frailty model

fitf <- coxph(Surv(time, status) ~ dm + htn + 
                age65 + dm*age65 + frailty(id, distribution="gaussian"), 
                data = set1)

summary(fitf)


# Fit a frailty model

fitg <- coxph(Surv(time, status) ~ dm + htn + 
                age65 + dm*age65 + frailty(id, distribution="gamma"), 
                data = set1)

summary(fitg)