Create a time series by 30 minute intervals

Question

I am trying to create a time series with 30 min intervals. I used the following command with the output also shown:

ts = seq(as.POSIXct("2009-01-01 00:00"), as.POSIXct("2014-12-31 23:30"),by = "hour") 

"2010-02-21 12:00:00 EST" "2010-02-21 13:00:00 EST" "2010-02-21 14:00:00 EST"

When I change it to by ="min" it changes to be every minute.

How do I create a time series with every 30 minute intervals?

Answer 1

You can specify minutes in the by argument, and pass the time zone "UTC" as Adrian pointed out. Check ?seq.POSIXt for more details about the by argument specified as a character string:

A character string, containing one of "sec", "min", "hour", "day", "DSTday", "week", "month", "quarter" or "year". This can optionally be preceded by a (positive or negative) integer and a space, or followed by "s".

ts <- seq(as.POSIXct("2017-01-01", tz = "UTC"),
    as.POSIXct("2017-01-02", tz = "UTC"),
    by = "30 min")
head(ts)

Output

[1] "2017-01-01 00:00:00 UTC"
[2] "2017-01-01 00:30:00 UTC"
[3] "2017-01-01 01:00:00 UTC"
[4] "2017-01-01 01:30:00 UTC"
[5] "2017-01-01 02:00:00 UTC"
[6] "2017-01-01 02:30:00 UTC"

Answer 2

Default units are seconds. So just do 1800 seconds to get 30 minutes.

ts = seq(as.POSIXct("2009-01-01 00:00"), as.POSIXct("2014-12-31 23:30"),by = 1800)

ts[1:20] [1] "2009-01-01 00:00:00 EST" "2009-01-01 00:30:00 EST" "2009-01-01 01:00:00 EST" "2009-01-01 01:30:00 EST" "2009-01-01 02:00:00 EST" [6] "2009-01-01 02:30:00 EST" "2009-01-01 03:00:00 EST" "2009-01-01 03:30:00 EST" "2009-01-01 04:00:00 EST" "2009-01-01 04:30:00 EST" [11] "2009-01-01 05:00:00 EST" "2009-01-01 05:30:00 EST" "2009-01-01 06:00:00 EST" "2009-01-01 06:30:00 EST" "2009-01-01 07:00:00 EST" [16] "2009-01-01 07:30:00 EST" "2009-01-01 08:00:00 EST" "2009-01-01 08:30:00 EST" "2009-01-01 09:00:00 EST" "2009-01-01 09:30:00 EST"