Calculate time difference between 2 timestamps in hours using R - r

Question

I'm trying to obtain the time difference between 2 timestamps in hours.
I have the data:
ID Lat Long Traffic Start_Time End_Time
1 -80.424 40.4242 54 2018-01-01 01:00 2018-01-01 01:10
2 -80.114 40.4131 30 2018-01-01 02:30 2018-01-01 02:40
3 -80.784 40.1142 12 2018-01-01 06:15 2018-01-01 07:20
I want to get the data like this
ID Lat Long Traffic Start_Time End_Time differ_hrs
1 -80.424 40.4242 54 2018-01-01 01:00 2018-01-01 01:10 00:50
2 -80.114 40.4131 30 2018-01-02 08:30 2018-01-02 08:40 01:10
3 -80.784 40.1142 12 2018-01-04 19:26 2018-01-04 20:11 01:15
I tried this code to capture the difference in hours:
df$differ_hrs<- difftime(df$End_Time, df$Start_Time, units = "hours")
However, it captures the difference like this:
ID Lat Long Traffic Start_Time End_Time differ_hrs
1 -80.424 40.4242 54 2018-01-01 01:00 2018-01-01 01:10 0.5
2 -80.114 40.4131 30 2018-01-02 08:30 2018-01-02 08:40 0.70
3 -80.784 40.1142 12 2018-01-04 19:26 2018-01-04 20:11 0.75
then I tried to set the difference in hours into format="%H%M" using the code:
df$differ_HHMM<- format(strptime(df$differ_hrs, format="%H%M"), format = "%H:%M")
But it produces all NAs.
So I decided to try a different way where I calculate the difference and set the format in the command itself adding "%H%M" like this:
df$differ_HHMM<- as.numeric(difftime(strptime(paste(df[,6]),"%Y-%m-%d %H:%M:%S"), strptime(paste(df[,5]),"%Y-%m-%d %H:%M:%S"),format="%H%M", units = "hours"))
but I keep getting the error message:
Error in difftime(strptime(paste(df[, 6]), "%Y-%m-%d %H:%M:%S"), strptime(paste(df[, :
unused argument (format = "%H:%M:%S")
Is there any way to calculate the time difference in %H:%M format?
I really appreciate your suggestions

Answer 1

The difference is a difftime class built on top of numeric. We could specify the units in difftime as seconds and use seconds_to_period from lubridate
library(lubridate)
df$differ_hrs<- as.numeric(difftime(df$End_Time, df$Start_Time,
units = "secs"))
out <- seconds_to_period(df$differ_hrs)
df$differ_HHMM <- sprintf('%02d:%02d', out#hour, out$minute)
NOTE: format works only on Date or Datetime class i.e. POSIXct, POSIXlt and not on numeric/difftime objects
data
df <- structure(list(ID = 1:3, Lat = c(-80.424, -80.114, -80.784),
Long = c(40.4242, 40.4131, 40.1142), Traffic = c(54L, 30L,
12L), Start_Time = structure(c(1514786400, 1514791800, 1514805300
), class = c("POSIXct", "POSIXt"), tzone = ""), End_Time = structure(c(1514787000,
1514792400, 1514809200), class = c("POSIXct", "POSIXt"), tzone = "")), row.names = c(NA,
-3L), class = "data.frame")