Believe it or not, it works either way: I haven't fully
figured out the logic yet (except to note that I had the
logic reversed below):
Ops.Date <- function (e1, e2)
{
if (nargs() == 1)
stop("unary ", .Generic, " not defined for Date objects")
boolean <- switch(.Generic, "<" = , ">" = , "==" = , "!=" = ,
"<=" = , ">=" = TRUE, FALSE)
if (!boolean)
stop(.Generic, " not defined for Date objects")
if (nchar(e1)) e1 <- as.Date(e1)
if (nchar(e2)) e2 <- as.Date(e2)
NextMethod(.Generic)
}
datechar1 = "1999-12-03"
datechar2 = "2000-12-07"
date1 = as.Date(datechar1)
date2 = as.Date(datechar2)
date1 == datechar1
datechar1 == date1
datechar1 < date2
date2 > datechar1
I also propose
as.Date.numeric <- function(x, ...) {
class(x) <- "Date"
x
}
this takes a number of seconds since 1970 and
converts it into a Date object ...
cheers
Ben
Gabor Grothendieck wrote:
> Note that the first argument still cannot be character
> since Ops.Date won't get dispatched in that case.
>
> On 6/24/06, Ben Bolker <[EMAIL PROTECTED]> wrote:
>> Ops.Date <- function (e1, e2)
>> {
>> if (nargs() == 1)
>> stop("unary ", .Generic, " not defined for Date objects")
>> boolean <- switch(.Generic, "<" = , ">" = , "==" = , "!=" = ,
>> "<=" = , ">=" = TRUE, FALSE)
>> if (!boolean)
>> stop(.Generic, " not defined for Date objects")
>> + if (!nchar(e1)) e1 <- as.Date(e1)
>> + if (!nchar(e2)) e2 <- as.Date(e2)
>> NextMethod(.Generic)
>> }
>>
>> adding the above two lines to Ops.Date makes, e.g.
>>
>> as.Date("1999-12-13") == "1999-06-14"
>>
>> behave as "expected".
>>
>> Does it seem like a good idea?
>> (I was inspired by a student's confusion, and by
>> the fact that Ops.factor does a similar thing -- although
>> in this case it seems more sensible to promote the
>> character to a Date rather than demoting the Date
>> to a character (in which case comparisons might not
>> work right?))
>>
>> Similar questions might apply to Ops.POSIXt ...
>>
>> Ben Bolker
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
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