How to convert a chron object to a numerical object of seconds since an origin in R

Question

I have a chron object like this:

 t <- as.chron("06/01/13 01:00:00", "%m/%d/%y %H:%M:%S")

and I want to convert it to seconds from origin, where the origin is:

 or <- "06/01/13 00:00:00"

so what I want is that the object t become:

 t <- 3600

Thank you very much Giulia

`as.numeric(t-as.chron("06/01/13 00:00:00", "%m/%d/%y %H:%M:%S"))*24*3600`? — Roland, Jan 10 '14 at 17:33

score 1 · Accepted Answer · answered Jan 10 '14 at 17:44

1

Just use difftime():

R> library(chron)
R>  t <- as.chron("06/01/13 01:00:00", "%m/%d/%y %H:%M:%S") 
R> or <- as.chron("06/01/13 00:00:00", "%m/%d/%y %H:%M:%S") 
R> difftime(t, or)
Time difference of 1 hours
R>

or in the units you want:

R> difftime(t, or, unit="secs")
Time difference of 3600 secs
R> as.numeric(difftime(t, or, unit="secs"))
[1] 3600
R>

As an aside, you probably want to use POSIXct instead of chron which difftime() converts to for you anyway. See help(DateTimeClasses).

answered Jan 10 '14 at 17:44

Dirk Eddelbuettel

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But beware that if you use POSIXct that you can then get subtle time zone problems which are not a problem if you stick with chron. – G. Grothendieck Jan 10 '14 at 19:00
Though in this case with straight differences that should not matter. – Dirk Eddelbuettel Jan 10 '14 at 19:06
Yes, its not likely that you will get in trouble with this specific operation but the implication is that you are using it more generally in which case you could. – G. Grothendieck Jan 10 '14 at 19:31

How to convert a chron object to a numerical object of seconds since an origin in R

1 Answers1