[R] Problem with timeSequence {timeDate} - wrong end date

[Benjamin B.]

Dear help-list,

I have a problem with timeSequence {timeDate}.

When I use it like

> timeSequence(from = "2008-01-01", to = "2010-12-13", by = "1 month")
GMT
 [1] [2008-01-01] [2008-02-01] [2008-03-01] [2008-04-01] [2008-05-01]
[2008-06-01] [2008-07-01] [2008-08-01] [2008-09-01] [2008-10-01]
[2008-11-01]
[12] [2008-12-01] [2009-01-01] [2009-02-01] [2009-03-01] [2009-04-01]
[2009-05-01] [2009-06-01] [2009-07-01] [2009-08-01] [2009-09-01]
[2009-10-01]
[23] [2009-11-01] [2009-12-01] [2010-01-01] [2010-02-01] [2010-03-01]
[2010-04-01] [2010-05-01] [2010-06-01] [2010-07-01] [2010-08-01]
[2010-09-01]
[34] [2010-10-01] [2010-11-01] [2010-12-01]

The result is as expected: a list of dates with all dates smaller then the
"to" date.

But somehow it behaves strange when I use it with a different starting date:

> test <- timeSequence(from = "2008-01-15", to = "2010-12-13", by = "1
month")
GMT
 [1] [2008-01-15] [2008-02-15] [2008-03-15] [2008-04-15] [2008-05-15]
[2008-06-15] [2008-07-15] [2008-08-15] [2008-09-15] [2008-10-15]
[2008-11-15]
[12] [2008-12-15] [2009-01-15] [2009-02-15] [2009-03-15] [2009-04-15]
[2009-05-15] [2009-06-15] [2009-07-15] [2009-08-15] [2009-09-15]
[2009-10-15]
[23] [2009-11-15] [2009-12-15] [2010-01-15] [2010-02-15] [2010-03-15]
[2010-04-15] [2010-05-15] [2010-06-15] [2010-07-15] [2010-08-15]
[2010-09-15]
[34] [2010-10-15] [2010-11-15] [2010-12-15]

In this case the last calculated date is obviously LARGER than the "to"
date:

> as.Date(test[length(test)]) < "2010-12-13"
[1] FALSE

This seem to occur also with other parameters:

> timeSequence(from = "1999-12-12", to = "2000-06-08", by = "2 months")
GMT
[1] [1999-12-12] [2000-02-12] [2000-04-12] [2000-06-12]

> timeSequence(from = as.Date("1999-12-12"), to = as.Date("2000-06-08"), by
= "2 months")
GMT
[1] [1999-12-12] [2000-02-12] [2000-04-12] [2000-06-12]

Am I missing something essential in using timeSequence?
Is this behavior wanted (then I don't get why it should...)?
Is there a better way to get those dates?

Thanks for reading and greetings,

Benjamin


Benjamin B.
Hamburg, Germany