The problem I am trying to solve is that I have a data frame with a sorted POSIXct variable in it. Each row is categorized and I want to get the time differences between eac
Try this:
library(dplyr)
df %>%
arrange(category, randtime) %>%
group_by(category) %>%
mutate(diff = randtime - lag(randtime),
diff_secs = as.numeric(diff, units = 'secs'))
# category randtime diff diff_secs
# (fctr) (time) (dfft) (dbl)
# 1 A 2015-06-01 11:10:54 NA hours NA
# 2 A 2015-06-01 15:35:04 4.402785 hours 15850.027
# 3 A 2015-06-01 17:01:22 1.438395 hours 5178.222
# 4 B 2015-06-01 08:14:46 NA hours NA
# 5 B 2015-06-01 16:53:43 518.955379 hours 1868239.364
# 6 B 2015-06-01 17:37:48 44.090950 hours 158727.420
You may also want to add replace(is.na(.), 0)
to the chain.