R help - Jan 2009 - Can I create a timeDate object using only year and week of the year values?

For a model I am working on, I have samples organized by year and week of
the year.  For this model, the data (year and week) comes from the basic
sample data, but I require a value representing the amount of time since the
sample was taken (actually, for the purpose of the model, it is sufficient
to use the number of weeks from the middle of the sample week to the
present).

What I have found so far includes:

library(Rmetrics)
time1 = timeDate(charvec = Sys.Date(), format = "%Y-%m-%d", zone =
"",
FinCenter = "")
time2 = timeDate("2004-08-30", format = "%Y-%m-%d", zone =
"", FinCenter "")
difftimeDate(time1,time2,units = "weeks")


Does timeDate use the format strings used by the UNIX date(1) command?  If
so, then can I safely assume timeDate will accept "%Y-%U-%w", and
behave
correctly?

Thanks,

Ted

	[[alternative HTML version deleted]]

On Tue, 27-Jan-2009 at 11:36AM -0500, Ted Byers wrote:


[....]


|> Does timeDate use the format strings used by the UNIX date(1)
|> command?  If so, then can I safely assume timeDate will accept
|> "%Y-%U-%w", and behave correctly?

Your chances are good.  To be sure, check out

?strptime

HTH

-- 
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>>>> "TB" == Ted Byers <r.ted.byers at gmail.com>
>>>> on Tue, 27 Jan 2009 11:36:22 -0500
   TB> What I have found so far includes:
   TB>
   TB> library(Rmetrics)
   TB> time1 = timeDate(charvec = Sys.Date(), format = %Y-%m-%d,
   TB> zone = ,
   TB> FinCenter = )
   TB> time2 = timeDate(2004-08-30, format = %Y-%m-%d, zone = ,
   TB> FinCenter    TB> )
   TB> difftimeDate(time1,time2,units = weeks)
   TB>
   TB>
   TB> Does timeDate use the format strings used by the UNIX date(1)
   TB> command?  If
   TB> so, then can I safely assume timeDate will accept %Y-%U-%w,
   TB> and behave
   TB> correctly?


Hi Ted,

timeDate uses internally the function 'strptime' to convert
the input charvec to the ISO time format.

As pointed out in the the manual page of 'strptime', the formats are
system-specific but should follow the ISO C / POSIX standard. Have a
look at ?strptime.

Hope this help,
Yohan


-- 
PhD student
Swiss Federal Institute of Technology
Zurich

www.ethz.ch