Thanks for the suggestion, Spencer. I will take a look and will report
to the list if I find this a better solution for my situation. Might
take a couple of days though.
Denis
Le 09-07-19 à 12:42, spencerg a écrit :
Have you considered the "timeDate" package?
Spencer
Denis Chabot wrote:
Thank you very much Duncan.
I'll follow your suggestion.
Why do I want to do what the designer did not think anyone would
want to do? I have data acquisition equipment taking measurements
every 15 min or so for days at a time, and I need to compile all
such experiments in a master data set. The data acquisition
equipment automatically switches to DST in spring and back to ST in
autumn, which I did not disable because it is easier to work with
while we are running the experiments.
I could use chron to ignore time zones and daylight savings time,
but this would not be of much help as whether or not I use
as.POSIXct or chron, there is one day of the year that has 25 h and
I need to deal with that 25th hour or I'll lose one hour of data!
Denis
Le 09-07-19 à 11:45, Duncan Murdoch a écrit :
On 19/07/2009 11:23 AM, Denis Chabot wrote:
[was " [R] end of daylight saving time"]
Hi,
I got no reply with the previous subject line, probably a bad
choice of subject on my part, so here it is again.
I read from the help on DateTimeClasses and various posts on this
list that, quite logically, one needs to specify if DST is
active or not when time is between 1 and 2 AM on the first
Sunday in November (for North America in recent years).
This I can do for on date at a time:
a <- as.POSIXct("2008-11-02 01:30:00", tz="EST5EDT") # to get
automatic use of DST
b <- as.POSIXct("2008-11-02 01:30:00", tz="EST") # to tell T
this is the second occurrence of 1:30 that day, in ST
difftime(b,a)
Time difference of 1 hours
But why can't I do the following, which appears to be a typical R
way of doing things, to handle several date-times at once?
c <- rep("2008-11-02 01:30:00", 2)
tzone = c("EST5EDT", "EST")
as.POSIXct(c, tz=tzone)
Erreur dans strptime(xx, f <- "%Y-%m-%d %H:%M:%OS", tz = tz) :
valeur 'tz' incorrecte
???
Objects of the POSIXlt and POSIXct classes don't support multiple
time zones, so if you specified several time zones on input, how
would the conversion functions decide which one to use for
output? You'll need to write your own wrapper function to make
this decision, and do the conversions separately for each input
timezone.
Why don't those classes support a separate time zone for each
entry? Presumably because their designer never thought anyone
would want to do that.
Duncan Murdoch
Thanks,
Denis Chabot
sessionInfo()
R version 2.9.1 Patched (2009-07-09 r48929)
x86_64-apple-darwin9.7.0
locale:
fr_CA.UTF-8/fr_CA.UTF-8/C/C/fr_CA.UTF-8/fr_CA.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods
base
loaded via a namespace (and not attached):
[1] tools_2.9.1
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.