IDate should not convert to Date when met with integers

[MichaelChirico]

There's a discrepancy between Date and IDate w.r.t. interacting with non-IDate objects, namely:

D <- as.Date("2016-02-09")
class(D + 1:3)

I <- as.IDate(D)
class(I + 1:3) #forced to `Date`

Is this intentional?

For reference, here is the +.Date method:

function (e1, e2) 
{
    coerceTimeUnit <- function(x) as.vector(round(switch(attr(x, 
        "units"), secs = x/86400, mins = x/1440, hours = x/24, 
        days = x, weeks = 7 * x)))
    if (nargs() == 1) 
        return(e1)
    if (inherits(e1, "Date") && inherits(e2, "Date")) 
        stop("binary + is not defined for \"Date\" objects")
    if (inherits(e1, "difftime")) 
        e1 <- coerceTimeUnit(e1)
    if (inherits(e2, "difftime")) 
        e2 <- coerceTimeUnit(e2)
    structure(unclass(e1) + unclass(e2), class = "Date")
}

[MichaelChirico]

Made progress on this but I can't seem to get the method to export properly. See this branch.

Any suggestions? I'm at a loss.

[jangorecki]

Looks like extra backtick in namespace file, easy visible when compare to master

export(as.IDate,as.ITime,IDateTime`)

[MichaelChirico]

oh, thanks! vestige from when I was trying to add it to exports.
On Apr 26, 2016 7:44 AM, "Jan Gorecki" [email protected] wrote:

extra backtick in namespace file, easy visible when compare to master

export(as.IDate,as.ITime,IDateTime`)

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#1528 (comment)

[WetRobot]

Hi,

I'm having some difficulties with the current -.IDate:

> d <- "2015-01-01"
> as.IDate(d) - 1.5
Error in as.Date.numeric(e2) : 'origin' must be supplied

because of forced coercion to Date. At the same time

> str(as.Date(d) - 1.5)
Date[1:1], format: "2014-12-30"

Might I suggest modifying the forced coercion to Date

return(`-.Date`(as.Date(e1),as.Date(e2)))

to just

return(`-.Date`(as.Date(e1), e2))

?

Then,

> str(as.IDate(d) - as.IDate(d))
int 0

> str(as.IDate(d) - 1L)
IDate[1:1], format: "2014-12-31"

> str(as.IDate(d) - as.Date(d))
IDate[1:1], format: "1970-01-01"
Warning message:
In str(as.IDate(d) - as.Date(d)) :
Incompatible methods ("-.IDate", "-.Date") for "-"

> str(as.IDate(d) - 1.0)
Date[1:1], format: "2014-12-31"

Side note: the warning message should perhaps not be a problem, since e.g.

> str(as.Date(d) - as.IDate(d))
Date[1:1], format: "1970-01-01"
Warning message:
In str(as.Date(d) - as.IDate(d)) :
Incompatible methods ("-.Date", "-.IDate") for "-"

and I at least would expect as.Date(d) - as.IDate(d) and as.IDate(d) - as.Date(d) to produce the same result even if it is broken.

[MichaelChirico]

Would you mind quickly trying it from my branch which has a different implementation of -.IDate?

[WetRobot]

You appear to have included difftime as a possible output and input of e2 - matter of taste perhaps, though of course more closely modeled after -.Date. Doubles work in your implementation as well, though should the output then be Date to conserve information?

> d <- "2015-01-01"

> str(as.IDate(d) - as.IDate(d))
Class 'difftime'  atomic [1:1] 0
  ..- attr(*, "units")= chr "days"

> str(as.IDate(d) - 1L)
 IDate[1:1], format: "2014-12-31"

> str(as.IDate(d) - as.Date(d)) 
 IDate[1:1], format: "1970-01-01"
Warning message:
In str(as.IDate(d) - as.Date(d)) :
  Incompatible methods ("-.IDate", "-.Date") for "-"

> str(as.IDate(d) - 1.0)
 IDate[1:1], format: "2014-12-31"

> str(as.IDate(d) - as.date(1))
 IDate[1:1], format: "2014-12-31"
Warning message:
In str(as.IDate(d) - as.date(1)) :
  Incompatible methods ("-.IDate", "Ops.date") for "-"

> diff <- as.Date(d) - (as.Date(d) - 10)
> str(as.IDate(d) - diff)
 IDate[1:1], format: "2014-12-22"
Warning message:
In str(as.IDate(d) - diff) :
  Incompatible methods ("-.IDate", "Ops.difftime") for "-"