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I would like to add 1 hour to a POSIXct object, but it does not support '+'.
This command:
as.POSIXct("2012/06/30","GMT") + as.POSIXct(paste(event_hour, event_minute,0,":"), ,"%H:%M:$S") returns this error:
Error in `+.POSIXt`(as.POSIXct("2012/06/30", "GMT"), as.POSIXct(paste(event_hour, : binary '+' is not defined for "POSIXt" objects How can I add a few hours to a POSIXct object ?
423
There are two POSIX date/time classes, which differ in the way that the values are stored internally. The POSIXct class stores date/time values as the number of seconds since January 1, 1970, while the POSIXlt class stores them as a list with elements for second, minute, hour, day, month, and year, among others.
time() can be used, and you can play around a bit with the basic types to get a feel for what R is doing. The as. POSIXct and as. POSIXlt commands are used to convert the time value into the different formats.
POSIXct stores date and time in seconds with the number of seconds beginning at 1 January 1970. Negative numbers are used to store dates prior to 1970. Thus, the POSIXct format stores each date and time a single value in units of seconds. Storing the data this way, optimizes use in data.
POSIXct objects are a measure of seconds from an origin, usually the UNIX epoch (1st Jan 1970). Just add the requisite number of seconds to the object:
x <- Sys.time() x [1] "2012-08-12 13:33:13 BST" x + 3*60*60 # add 3 hours [1] "2012-08-12 16:33:13 BST" If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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