Calculate number of days between two dates in r

Question

I need to calculate the number of days elapsed between multiple dates in two ways and then output those results to new columns: i) number of days that has elapsed as compare

Answer 1

You can just add each column with the simple difftime and lagged diff calculations.

DATA$FIRST <- c(0, 
                with(DATA, 
                     difftime(DATE[2:length(DATE)],DATE[1], unit="days")
                     )
                )
DATA$BETWEEN <- c(0, 
                  with(DATA, 
                       diff(DATE[1:(length(DATE) - 1)], unit="days")
                       )
                  )

identical(DATA, RESULTS)
[1] TRUE