time variable .

[aliman]

Hello,
I have a time series with one variable naturally being date/time.
I split the date/time into 2 variables one being date and the other time using
temp_HR=temp_HR%>%mutate(date=as.Date(recorded_dttm))
temp_HR=temp_HR%>%mutate (time=format(as.POSIXct(recorded_dttm) ,format = "%H:%M:%S"))

now, I want to create a new variable with the time difference between consecutive elements. However the time variable generated above is in character format.

any advice?
thank youo.

[FJCC]

Wouldn't it be easier to directly take the difference between the datetimes?

[aliman]

sure, how would I do that?

[FJCC]

Here is an example with print statements after each step so you can see the logic of the code.

library(dplyr)
DF <- data.frame(DateTime = as.POSIXct(c("2020-04-01 00:00:00",
                                         "2020-04-01 00:23:02",
                                         "2020-04-01 01:45:15",
                                         "2020-04-01 9:41:18")))
DF
#>              DateTime
#> 1 2020-04-01 00:00:00
#> 2 2020-04-01 00:23:02
#> 3 2020-04-01 01:45:15
#> 4 2020-04-01 09:41:18
DF <- DF %>%  mutate(DateTimeLag = lag(DateTime))
DF
#>              DateTime         DateTimeLag
#> 1 2020-04-01 00:00:00                <NA>
#> 2 2020-04-01 00:23:02 2020-04-01 00:00:00
#> 3 2020-04-01 01:45:15 2020-04-01 00:23:02
#> 4 2020-04-01 09:41:18 2020-04-01 01:45:15
DF <- DF %>% mutate(Interval = DateTime - DateTimeLag)
DF
#>              DateTime         DateTimeLag       Interval
#> 1 2020-04-01 00:00:00                <NA>        NA mins
#> 2 2020-04-01 00:23:02 2020-04-01 00:00:00  23.03333 mins
#> 3 2020-04-01 01:45:15 2020-04-01 00:23:02  82.21667 mins
#> 4 2020-04-01 09:41:18 2020-04-01 01:45:15 476.05000 mins

^{Created on 2020-04-08 by the reprex package (v0.3.0)}

[aliman]

@FJCC

as.POSIXct

thank you. for some reason the intervals don't make sense in my case
for example the difference between 2018-08-21 17:04:00 and 2018-08-21 17:15:00 is coming out as 660.

[aliman]

nevermind its just in seconds.
thanks for the help

[technocrat]

Great. Please mark the solution for the benefit of those to follow.

For future similar date work, take a look at the lubridate package, which has a duration object that can make date calculations easier.