Find the last date in a column of dates in R

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I have a column of start and stop dates, and I need to extract the latest (most recent) stop date in order to calculate duration. (earliest start date - latest stop date) Unfortunately, the dates in the last column are not necessarily the latest dates. So, I would have to go by row and compare the dates to figure out the latest date. The other caveat is that not all columns will have dates.

Here's an example column of dates:

pacman::p_load(tibble, lubridate)

start_1 <- as_tibble(sample(seq(ymd("1999/01/01"), ymd("2000/01/01"), by="day"), 5))
stop_1 <- as_tibble(sample(seq(ymd("2000/01/01"), ymd("2001/01/01"), by="day"), 5))
stop_2 <- as_tibble(c(ymd("2000/03/05"), ymd("2000/11/15"), ymd("2000/07/22"), ymd("2000/05/05"), NA))
stop_3 <- as_tibble(c(ymd("2000/12/12"), ymd("2000/02/09"), NA, NA, NA))

dat <- cbind(start_1, stop_1, stop_2, stop_3)

I really have no idea how to go about this, and would appreciate any help.

Thank you!

r date
2 Answers

One option is to use apply():

durs = as.Date(apply(dat[,c(2:ncol(dat))],1,max,na.rm=T))-dat[,1]

This assumes that the first column contains the start date and all columns thereafter contain possible stop dates.

user_180842730

First fix the column names and then use rowwise() with c_across().

colnames(dat) = c("start_1", "stop_1", "stop_2", "stop_3")

dat %>% 
  rowwise() %>%
  mutate(LastDate=max(c_across(starts_with("stop")), na.rm=T),
         Duration = LastDate-start_1)


  start_1    stop_1     stop_2     stop_3     LastDate   Duration
  <date>     <date>     <date>     <date>     <date>     <drtn>  
1 1999-10-20 2000-11-12 2000-03-05 2000-12-12 2000-12-12 419 days
2 1999-04-30 2000-05-05 2000-11-15 2000-02-09 2000-11-15 565 days
3 1999-05-01 2000-04-01 2000-07-22 NA         2000-07-22 448 days
4 1999-04-17 2000-08-23 2000-05-05 NA         2000-08-23 494 days
5 1999-04-10 2000-04-02 NA         NA         2000-04-02 358 days
user_44475400
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