R programming loop difference

Question

I have two variables and I would like to loop them such that, it should calculate arrival of(i) - departure of (i+1) and it should store the result in a new column

departure                            arrival
2012-01-26 08:15:00                 2012-01-26 08:50:00
2012-01-26 11:30:00              2012-01-27 16:00:00
2012-01-27 18:00:00               2012-01-27 23:05:00
2012-02-11 00:20:00                 2012-02-11 09:10:00

expected output
waiting time
(2012-01-26 08:50:00)-(2012-01-26 11:30:00) =  2 hr 40 min
 (2012-01-27 16:00:00)-( 2012-01-27 18:00:00) =  2 hrs
 (2012-01-27 23:05:00)- (2012-02-11 00:20:00)=14 days 13 hrs, 349 hrs

I tried this, but I kept getting errors:

for (i :length(data frame){
i <- i[17] #index of arrival column
j <- i+1[18] #index of departure column
diff = i-j
return diff
}
diff = waiting time

Answer 1

Use the lubridate package to do this:

d$departure <- lubridate::ymd_hms(d$departure)
d$arrival   <- lubridate::ymd_hms(d$arrival)

d$difference <- d$departure - d$arrival
d