[R] Bug in seq.date?

[Gabor Grothendieck]

Note that chron does give the last day of the month:

> library(chron)
> seq(chron("1/31/2000"), chron("1/31/2001"), "month")
 [1] 01/31/00 02/29/00 03/31/00 04/30/00 05/31/00 06/30/00 07/31/00 08/31/00
 [9] 09/30/00 10/31/00 11/30/00 12/31/00 01/31/01

The zoo package has a "yearmon" class whose as.Date.yearmon can
convert a "Date" to the end of the month:
library(zoo)
> library(zoo)
> as.Date(as.yearmon(seq(as.Date("2000-1-31"), as.Date("2001-1-31"), "month")), 1)
 [1] "2000-01-31" "2000-02-29" "2000-03-31" "2000-04-30" "2000-05-31"
 [6] "2000-06-30" "2000-07-31" "2000-08-31" "2000-09-30" "2000-10-31"
[11] "2000-11-30" "2000-12-31" "2001-01-31"

And we do it ourself like this:

> as.Date(format(seq(as.Date("2000-1-1"), as.Date("2001-1-1"), "month") + 32, "%Y-%m-01"))-1
 [1] "2000-01-31" "2000-02-29" "2000-03-31" "2000-04-30" "2000-05-31"
 [6] "2000-06-30" "2000-07-31" "2000-08-31" "2000-09-30" "2000-10-31"
[11] "2000-11-30" "2000-12-31" "2001-01-31"




On 6/4/07, hadley wickham <h.wickham at gmail.com> wrote:
> > seq(as.Date("2000-1-1"), as.Date("2001-1-1"), "months")
>  [1] "2000-01-01" "2000-02-01" "2000-03-01" "2000-04-01" "2000-05-01"
>  [6] "2000-06-01" "2000-07-01" "2000-08-01" "2000-09-01" "2000-10-01"
> [11] "2000-11-01" "2000-12-01" "2001-01-01"
>
>
> > seq(as.Date("2000-1-31"), as.Date("2001-1-31"), "months")
>  [1] "2000-01-31" "2000-03-02" "2000-03-31" "2000-05-01" "2000-05-31"
>  [6] "2000-07-01" "2000-07-31" "2000-08-31" "2000-10-01" "2000-10-31"
> [11] "2000-12-01" "2000-12-31" "2001-01-31"
>
> Is this a bug?
>
> Hadley
>
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