[R] Finicky factor comparison operators

[R. Michael Weylandt]

It's not a matter of unordered & ordered factors, but ordered factors
and Dates (as the warning says)

I can see at least one ambiguity -- should comparison be made from the
level or the internal code -- so the warning makes sense to me (though
an error might make even more sense). Generally, for factors that
correspond to non-Date quantities, the comparison likely isn't well
defined.

How would you resolve this comparison in general?

Michael

On Sat, Feb 18, 2012 at 3:08 PM, johnmark <johnmark.agosta at gmail.com> wrote:
>  This error occurs because the "==" comparison operator doesn't allow
> comparison of ordered and normal factors:
>
> /df[df5$close_quarter == as.Date("2011-02-01"),]/
> Warning message:
> In /`[.data.frame`(df, df$close_quarter == as.Date("2011-02-01")/,  :
>  Incompatible methods ("Ops.ordered", "Ops.Date") for "=="
>
> Why should this be a problem -- Isn't this being overly cautious?  Can
> anyone think of a case where coercing the ordered factor to a normal factor
> for comparisons of == would do the wrong thing?
>
> Perhaps this is a question for the developer's section.
>
> Cheers -john mark agosta
>
>
>
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