Hello,
I have a data frame containing time (e.g. GMT), and I would like to
create/add a new variable that would be the computation of the elapsed
time since the first observation. Does anyone have a suggestion for an
easy way to do this? I am having trouble creating a new variable that
would contain just the first time observation (then I could take
difference between actual time and initial time).
e.g. - here's a brief representation of the data:
time <-
c("19:36:11","19:36:12","19:36:13","19:36:14","19:36:15","19:36:16")
strptime(time, "%H:%M:%S")
y<-c(197,194,189,179,166,150)
mydata<-data.frame(time=time,y=y)
OK, now how do I create a new variable, say, time_el, that would
calculate the elapsed time since 19:36:11? I assume that I need the
strptime() function to make sure R treats the character strings as time.
Thank you very much for any & all assistance!
-Philippe
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