-- begin included message --
I am trying to set up a data set for a survival analysis with time-varying
covariates. The data is already in a long format, but does not have a variable
to signify the stopping point for the interval. The variable DaysEnrolled is
the
variable I would like to use to form this interval. This is what I have now:
...
---- end inclusion
I would have expected a dozen solutions from the list - data manipulation
problems usually get a large following. It can be done in 4 lines, assuming
that the parent data set is sorted by subject and time within subject.
newdata$start <- olddata$DaysEnrolled #start time = the current variable
temp <- olddata$DaysEnrolled[-1] # shift column up by one position
temp[diff(olddata$id) !=0] <- NA # NA for last line of each subject
newdata$stop <- c(temp, NA) # add the NA for the last subject
I will leave it to others to compress this into a 1-line application of one
of the apply functions. (Unreadable perhaps, but definitely more elegant :-)
Terry T.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
