[Rd] Extract/format/show for S4 objects

[Gabor Grothendieck]

Note that zoo's merge can handle that:

>> library(zoo)
> z <- zooreg(1:6, as.yearqtr("2000 Q1"))
> merge(z, zlag = lag(z1, -1))
        z  zlag
2000 Q1  1   NA
2000 Q2  2    1
2000 Q3  3    2
2000 Q4  4    3
2001 Q1  5    4
2001 Q2  6    5
2001 Q3 NA    6



On Wed, Jun 9, 2010 at 10:09 AM, Johann Hibschman <jhibschman at gmail.com> wrote:
> Gabor Grothendieck <ggrothendieck at gmail.com> writes:
>
>> The yearqtr class already rounds off automatically to avoid floating
>> point effects and handles #1 and #2.
>
> The main use for all this was so I could use quarters as index columns
> with data.table, which demands integer storage mode.  (This is part of
> my ongoing attempt to reinvent q/kdb+ in R.)
>
> I've had some problems with yearmon's conversions in the past, so I'm
> (probably unfairly) suspicious of the approach of storing dates as
> floats.  To be fair, once I reported the bug, it was fixed almost
> immediately; I was very impressed.
>
>> On the other hand if you are just interested in playing around with S4
>> for its own sake review the source code of the mondate package as an
>> example of an S4 based date package.
>
> Thanks, that's a very useful example.  I don't understand all of what's
> going on in there, but I find it easier to understand the documentation
> with an example in hand.
>
> Cheers,
> Johann
>
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