[R] Keep only first date from consecutive dates

Frank S.
2015-12-04T20:53:49Z

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.





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