SurvtoLR: Transform Surv object to data matrix with L and R columns
Description
Take a Surv object and transforms it into a data matrix with two columns, L and R,
representing the left and right points of observed time intervals. For right-censored data, R = NA.
The input Surv object should be in the form of Surv(L,R,type='interval2'), where R = NA for right-censored data.
References
Michael P. Fay, Pamela A. Shaw (2010). Exact and Asymptotic Weighted Logrank Tests for Interval Censored Data: The interval R Package.
Journal of Statistical Software, 36 1-34.