In rereading my post, he as.Date(x)+as.Date(y) part of
the equivalence should be removed. The rest of it
is ok.
Date: Mon, 22 Mar 2004 17:35:27 -0500 (EST)
From: Gabor Grothendieck <ggrothendieck@myway.com>
To: <R-devel@stat.math.ethz.ch>
Subject: [Rd] as.Date.numeric
Regarding the new R 1.9.0 Date class, it would be nice to have
as.Date.numeric .
1. as.numeric(x) works for Date objects and it would be convenient
to also have the inverse.
2. It leads to some nice additive properties for integer x and y:
as.Date(x+y) = as.Date(x) + as.Date(y)
= as.Date(x) + y = as.Date(y) + x
3. It gives a pleasing way to quickly get the origin:
as.Date(0)
4. The corresponding ability is already available in chron,
e.g. chron(0), and I have found that I did make use of it
in my work with chron.
5. Its particularly convenient in testing since you can quickly
generate a sequence of dates like this:
as.Date(1:100)
Its quite simple to implement:
as.Date.numeric <- function(x) structure( floor(x), class = "Date"
)