Re: [R] Recoding dates to session id in a longitudinal dataset

2010-06-27 Thread JP Bogers
Hi Jim, Thanks for the answer. What I actually want is a session sequence 1,2,... per patient. This would be very useful to look at trends of HPV infections from the first to the second sample etc. It would also allow me to extract the HPV data of the first sample (session 1). Thx JP On Sat,

[R] Recoding dates to session id in a longitudinal dataset

2010-06-26 Thread John-Paul Bogers
Hi, I'm fairly new to R but I have a large dataset (30 obs) containing patient material. Some patients came 2-9 times during the three year observation period. The patients are identified by a unique idnr, the sessions can be distinguished using the session date. How can I recode the date of

Re: [R] Recoding dates to session id in a longitudinal dataset

2010-06-26 Thread John-Paul Bogers
-- Forwarded message -- From: John-Paul Bogers john-paul.bog...@ua.ac.be Date: Sat, Jun 26, 2010 at 10:14 PM Subject: Re: [R] Recoding dates to session id in a longitudinal dataset To: jim holtman jholt...@gmail.com Dear Jim, he data concerns HPV screening data. The data looks