问题
I've encountered the following error when converting a set of dates in character format to a POSIXct object.
Example Data:
t<-c("3/11/2007 1:30", "3/11/2007 2:00", "4/11/2007 2:00")
str(t)
chr [1:3] "3/11/2007 1:30" "3/11/2007 2:00" "4/11/2007 2:00"
z<-as.POSIXct(strptime(t, format ="%m/%d/%Y %H:%M"))
z
"2007-03-11 01:30:00 MST" NA "2007-04-11 02:00:00 MDT"
str(z)
POSIXct[1:3], format: "2007-03-11 01:30:00" NA "2007-04-11 02:00:00"
My question is why is the NA returned for the second date in z? I have a dataset that contains 8 years of hourly data (from which I copied the dates above), and this NA error pops up only for dates between 3/8 - 3/14 and ONLY when the hour is 02:00:00.
I do not encounter an error if the dates are converted to POSIXlt, so that is my current work around.
Any thoughts?
回答1:
Try using a time zone that does not use daylight savings time:
as.POSIXct(t, format = "%m/%d/%Y %H:%M", tz = "GMT")
## [1] "2007-03-11 01:30:00 GMT" "2007-03-11 02:00:00 GMT" "2007-04-11 02:00:00 GMT"
来源：https://stackoverflow.com/questions/27624947/posixct-date-conversion-error