[R] given a mid-month date, get the month-end date
Spencer Graves
spencer.graves at pdf.com
Mon Dec 19 19:08:30 CET 2005
If you work much with time data and time series data and you have not
already mastered the "zoo" package, you may be interested in a small
testimonial from one unfamiliar with the names of Achim Zeileis and
Gabor Grothendieck two years ago: The package itself seems to have many
useful features, filling an important gap in other capabilities, AND
vignette("zoo") makes it relatively easy to learn.
Those unfamiliar with vignettes in R may wish to know that the command
> (zoo.vignette <- vignette("zoo"))
will open an Adobe Acrobat file containing a narrative overview of the
package's capabilities. The R commands used in the file can be easily
obtained in a script file after this command via
> edit(zoo.vignette)
in RGui; this should open the R comands in an editor script window.
This may not have the desired effect in XEmacs, which I use. Instead, I
use the following:
> Stangle(zoo.vignette$file)
This writes the R commands to file zoo.R in the working directory. From
there, I then use menu File -> Open -> “zoo.R”.
hope this helps.
Spencer Graves
p.s. In case it's not completely obvious from the above, I wish to here
extend my thanks and complements to Achim Zeileis and Gabor Grothendieck
for a great package with good documentation.
Gabor Grothendieck wrote:
> The zoo package has a yearmon class with as methods which can be
> used:
>
> library(zoo)
> dd <- Sys.Date() # test data
>
> as.Date(as.yearmon(dd), frac = 1)
>
> as.yearmon converts the "Date" class date to a year and month of
> class "yearmon" dropping the day and representing it internally in
> a way consistent with "ts" class.
>
> as.Date above then converts it back to "Date" class.
> Since yearmon dates have no day (they are just a year and
> a month) the frac argument is used to indicate what fraction
> of the month to use as the day of the month so frac = 0 (the
> default) would give the beginning of the month) and frac = 1
> gives the end.
>
> On 12/19/05, t c <quantpm at yahoo.com> wrote:
>
>> I have a vector of dates.
>>
>> I wish to find the month end date for each.
>>
>> Any suggestions?
>>
>> e.g.
>>
>> For 12/15/05, I want 12/31/05,
>>
>> For 10/15/1995, I want 10/31/1995, etc
>>
>>
>>__________________________________________________
>>
>>
>>
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>
>
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--
Spencer Graves, PhD
Senior Development Engineer
PDF Solutions, Inc.
333 West San Carlos Street Suite 700
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spencer.graves at pdf.com
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