# framingham data -- in 2 year slices

ds = read.table("framDataR.txt",header=T)

ds$chol.z = (ds$chol - mean(ds$chol))/sd(ds$chol)

# product, in order to model changing beta for cholesterol

ds$chol.z.fu.year = ds$chol.z * ( (ds$age.from+1) - ds$age )

ds[1:10,]


# load survival package

  require(survival)
  
   # don't ask for exact methods with this many ties!!
  
  fit=coxph(Surv(age.from,age.to,case) ~ chol.z + chol.z.fu.year, data=ds )

 # constant HR over follow-up time 

   fitConstantHR =coxph(Surv(age.from,age.to,case) ~ chol.z , data=ds ); 

   summary(fitConstantHR)

 
 # log(HR) linear over follow-up time 

  fitLinearLogHR = coxph(Surv(age.from,age.to,case) ~ chol.z + chol.z.fu.year, 
                  data=ds ); 

   summary(fitLinearLogHR)