[R] Applying strptime() to a data set or array
ggrothendieck at gmail.com
Tue Mar 7 06:42:17 CET 2006
POSIXct, not POSIXlt, are used in data frame columns.
See ?POSIXct where this is mentioned and try:
A$date <- as.POSIXct(A$date)
Also be sure to read R News 4/1 for more about dates and times.
On 3/6/06, Andrew Athan <aathan_R_1542 at memeplex.com> wrote:
> I'm sure this is just the result of a basic misunderstanding of the
> syntax of R, but I am stumped.
> A <-
> A now consists of thousands of rows, but A$date is a string...
> 3183 2006-02-28 12:00:00 548.470
> 3184 2006-02-28 12:30:00 515.240
> 3185 2006-02-28 13:00:00 140.120
> 3186 2006-02-28 13:30:00 450.940
> 3187 2006-02-28 14:00:00 318.570
> So, I try to convert A$date to a POSIXlt ...
> A[,1]<-strptime(A$date,"%Y-%m-%d %H:%M:%s")
> A$date<-strptime(A$date,"%Y-%m-%d %H:%M:%s")
> which gives me a warning that the length of the array I am trying to
> replace A$date with is 9 ... but if I print strptime(A$date,"%Y-%m-%d
> %H:%M:%s"), it clearly has thousands of rows. Yet, if I ask for
> length(strptime(A$date,"%Y-%m-%d %H:%M:%s")), I get 9.
> What am I doing wrong? Do I need to convert the return value of
> strptime(A$date,"%Y-%m-%d %H:%M:%s") to some array/vector/matrix
> datatype before attempting to assign it?
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