On 9/17/2008 1:24 PM, Lee, Philip (IT) wrote:
r-devel,

I've been trying to write a C plugin for R, and I'm struggling to
understand how dates are represented.

I can create a date in R:
mydate<-as.Date(1, origin="1900-01-01") mydate
[1] "1900-01-02"

See ?Date for the internal represention: it's a count of days from a particular epoch.

When I pass my date to a plugin, though, it's type is that of a real.
There doesn't seem to be a date type in Rinternals.h, is there a way to
recognize that a value is a date rather than a real?

Look at the class attribute.

Equally, does anyone know if it's possible to create date values in the
C api?

Create a vector of doubles, and attach the right class to it. See section 5.8.5 of the R extensions manual for an example.

Duncan Murdoch


Thanks,
Phil Lee

Philip Lee
Morgan Stanley | Technology
750 Seventh Avenue, 12th Floor | New York, NY  10019
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