[R] having trouble extracting week from chron object

[David Winsemius]

On Aug 30, 2011, at 1:36 PM, Christopher W Ryan wrote:

> Running R 2.13.1 on Windows XP.
> I would like to get week of the year (1-52) for each date.
>
> library(chron)
> dts <- dates(c("02/27/92", "02/27/92", "01/14/92","02/28/92",  
> "02/01/92"))
> dts
> dts.chron <- as.chron(dts)
> dts.chron
> class(dts.chron)
> # all of these component extractions work:
> months(dts.chron)
> weekdays(dts.chron)
> years(dts.chron)
> quarters(dts.chron)
> # but weeks() doesn't seem to work

It doesn't "work" for me either but since I also have the package  
lubridate loaded, and ?weeks brings up a lubridate help page, I don't  
feel I have any right to complain. I get an error message.... what did  
you get?:

Error in Ops.dates(pieces$week, 7) : * not defined for chron objects

If I were posting I would also have had the good sense to include the  
output of sessionInfo().

> weeks(dts.chron)

Try type just:

  weeks  # I get a lubridate function.

>
> ?chron tells me:


Bur what does ?weeks tell you?

> . . . The functions days(), months(), quarters(),
> years(), weeks(), weekdays(), hours(), minutes(), and seconds() take
> any chron object as input and extract the corresponding time interval
> . . . .
>
> Any advice?
>
> Thanks.
>
> Chris Ryan
> SUNY Upstate Medical University Clinical Campus at Binghamton
> Binghamton, NY
>
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David Winsemius, MD
West Hartford, CT