With a data.frame sorted by id, with ties broken by date, as in
your example, you can select rows that are either the start
of a new id group or the start of run of consecutive dates with:
> w <- c(TRUE, diff(uci$date)>1) | c(TRUE, diff(uci$id)!=0)
> which(w)
[1] 1 4 5 7
> uci[w,]
id date value
1 1 2005-10-28 1
4 1 2005-11-07 3
5 1 2007-03-19 1
7 2 2004-06-02 2
I'll leave it to you to translate that R syntax into data.table syntax -
it just involves comparing the current row with the previous row.
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Fri, Dec 4, 2015 at 12:53 PM, Frank S. <f_j_...@hotmail.com> wrote:
> Dear R users,
>
> I usually work with data.table package, but I'm sure that muy question can
> also be answered working with R data frame.
> Working with grouped data (by "id"), I wonder if it is possible to keep in a
> R data.frame (or R data.table):
> a) Only the first row if there is a row which belongs to a a group of rows
> (from same "id") that have consecutive dates.
> b) All the rows which do not belong to the above groups.
>
> As an example, I have "uci" data.frame:
>
> uci <- data.table(id=c(rep(1,6),2),
> date =
> as.Date(c("2005-10-28","2005-10-29","2005-10-30","2005-11-07","2007-03-19","2007-03-20","2004-06-02")),
> value = c(1, 2, 1, 3, 1, 2, 2))
>
> id date value
> 1 2005-10-28 1
> 1 2005-10-29 2
> 1 2005-10-30 1
> 1 2005-11-07 3
> 1 2007-03-19 1
> 1 2007-03-20 2
> 2 2004-06-02 2
>
> And the desired output would be:
>
> id date value
> 1 2005-10-28 1
> 1 2005-11-07 3
> 1 2007-03-19 1
> 2 2004-06-02 2
>
> # From the following link, I have tried:
> http://stackoverflow.com/questions/32308636/r-how-to-sum-values-from-rows-only-if-the-key-value-is-the-same-and-also-if-the
>
> setDT(uci)[ ,list(date=date[1L], value = value[1L]), by = .(ind=rleid(date),
> id)][, ind:=NULL][]
>
> But I get the same data frame, and I do not know the reason.
>
> Thank you very much for any help!!
>
> Frank S.
>
>
>
>
>
> [[alternative HTML version deleted]]
>
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