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

[Joshua Wiley]

Dear Benjamin,

timeSequence() ultimately is relying on seq.POSIXt().  If you look at
the last paragraph of the "Details" section in ?seq.POSIXt it seems to
basically indicate that using by = "month" just sequences through the
months and the day is only changed if it is invalid for a particular
month (the relevant lines are around 88--100 in the seq.POSIXt code).

It is fairly straightforward ensure the output is less than "to".
Here is one option:

test <- timeSequence(from = "2008-01-01", to = "2010-12-13", by = "1 month")
test <- test[as.Date(test) < as.Date("2010-12-13")]
test

Cheers,

Josh


On Thu, Jan 6, 2011 at 1:30 AM, Benjamin B. <benj.bad.ac at googlemail.com> wrote:
> 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
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/