On Mon, Feb 9, 2009 at 4:57 PM, <[email protected]> wrote:
>
> hi,
>
> I have some session data in a dataframe, where each session is recorded with
> a start and a stop date. Like this:
>
> session_start session_stop
> ===================
> 2009-01-03 2009-01-04
> 2009-01-01 2009-01-05
> 2009-01-02 2009-01-09
>
> A session is at least one day long. Now I want a dataframe with 'active
> sessions' per date. Like this:
>
> date active_sessions
> =============
> 2009-01-01 1
> 2009-01-02 2
> 2009-01-03 3
> 2009-01-04 3
> 2009-01-05 2
> 2009-01-06 1
> 2009-01-07 1
> 2009-01-08 1
> 2009-01-09 1
>
> How do I do that? I've searched the usual sources, but my newbie status and
> language barrier left me with nothing. So plz, anyone?
>
Hej Stefan,
The following should do. It's a bit convoluted though, so someone else
might be able to come up with a better solution.
> test
start stop
1 2009-01-03 2009-01-04
2 2009-01-01 2009-01-05
3 2009-01-02 2009-01-09
activeDaysPerSession<-apply(test,MARGIN=1,FUN=function(x)
seq(from=as.Date(x["start"]),
to=as.Date(x["stop"]),by=1
)
)
ActiveDays<-as.Date(unlist(activeDaysPerSession))
as.data.frame(table(ActiveDays))
Regards,
Gustaf
--
Gustaf Rydevik, M.Sci.
tel: +46(0)703 051 451
address:Essingetorget 40,112 66 Stockholm, SE
skype:gustaf_rydevik
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