[R] zoo: bug with unique for yearmon

[Achim Zeileis]

On Mon, 9 Nov 2009, Achim Zeileis wrote:

> On Mon, 9 Nov 2009, Johann Hibschman wrote:
>
>> I'm using R 2.10.0, with zoo 1.5-8. The release notes for zoo 1.5-8
>> claim a bug with unique for yearmon objects has been fixed, but I'm
>> still having problems.
>
> 1. Please report such problems (also) to the maintainers and not (only)
>   to the list.
> 2. Please provide a reproducible example.
> 3. Both of the points above are pointed out in the posting guide.

Just as a follow-up to the list: The original poster provided a small 
reproducible example off-list, the package authors could identify and fix 
the problem (in the - method), an improved version is already on R-Forge 
and will be committed in the next days to CRAN. Sometimes life with 
open-source software can be so easy ;-)
Z

>> Browse[1]> tmp2
>> [1] "Dec 1996" "Dec 1996"
>> Browse[1]> unique(tmp2)
>> [1] "Dec 1996" "Dec 1996"
>> Browse[1]> unique(unique(tmp2))
>> [1] "Dec 1996"
>> Browse[1]> as.numeric(tmp2) - (1996 + 11/12)
>> [1]  0.000000e+00 -2.273737e-13
>
> A "proper" yearmon object should take care of this and have a unique 
> representation of Dec 1996. But to understand what went wrong, we need to 
> understand how that malformed Dec 1996 object was created.
> Z
>
>> Is there a work-around? I had been using an integer months-since-2000
>> as my month index, so I can go back to doing that, but it's much
>> harder to interpret those numbers.
>> 
>> Clearly, I'm being bitten by the floating-point representation, but
>> the only "complex" thing I did was to manually lag a time series by
>> assigning date <- date + 1/12, and I was hoping that the yearmon class
>> would apply some magic to normalize the representation.
>> 
>> Regards,
>> Johann Hibschman
>> 
>> ______________________________________________
>> R-help at 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.
>> 
>> 
>