Re: [R] Time interactions for coxph object

2014-04-08 Thread Therneau, Terry M., Ph.D.
The very first step is to understand the possible nature of proportional hazards. This is parallel to the usual advice in linear models to graph the data before you start fitting complicated non-linear models. zp <- cox.zph(CSHR.shore.fly, transform="identity") plot(zp)# or plot(zp[3]) f

Re: [R] Time interactions for coxph object

2014-04-07 Thread David Winsemius
On Apr 7, 2014, at 9:36 AM, Tim Marcella wrote: Hi All, I am working in the 'survival' library and need to know how to code a variable time interaction for left truncated data (not all subjects followed from the start of the study). I therefor add in the entry time and exit time variables i

[R] Time interactions for coxph object

2014-04-07 Thread Tim Marcella
Hi All, I am working in the 'survival' library and need to know how to code a variable time interaction for left truncated data (not all subjects followed from the start of the study). I therefor add in the entry time and exit time variables into the formula. Here is my basic formula CSHR.sh