[R] Counting session days

[Gabor Grothendieck]

Try this:

> dateseq <- function(i) seq(DF[i, 1], DF[i, 2], 1)
> table(as.Date(unlist(lapply(1:nrow(DF), dateseq)), origin = "1970-01-01"))

2009-01-01 2009-01-02 2009-01-03 2009-01-04 2009-01-05 2009-01-06 2009-01-07
         1          2          3          3          2          1          1
2009-01-08 2009-01-09
         1          1

On Mon, Feb 9, 2009 at 10:57 AM,  <stefan.petersson at inizio.se> 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?
>
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