Does the following example help? isFirstInRun() and isLastInRun() are handy
utility functions.
> d <- transform(data.frame(Date=as.Date(c("2016-01-05", "2016-03-04",
"2016-03-30", "2015-12-02", "2016-03-04", "2015-12-21"))),
DaysSince1970=as.integer(Date), I=seq_along(Date))
> d
Date DaysSince1970 I
1 2016-01-05 16805 1
2 2016-03-04 16864 2
3 2016-03-30 16890 3
4 2015-12-02 16771 4
5 2016-03-04 16864 5
6 2015-12-21 16790 6
> isFirstInRun <- function(x) c(TRUE, x[-1] != x[-length(x)])
> isLastInRun <- function(x) c(x[-1] != x[-length(x)], TRUE)
> ds <- d[order(d$Date),]
> ds
Date DaysSince1970 I
4 2015-12-02 16771 4
6 2015-12-21 16790 6
1 2016-01-05 16805 1
2 2016-03-04 16864 2
5 2016-03-04 16864 5
3 2016-03-30 16890 3
> ds[isFirstInRun(format(ds$Date, "%Y-%m")),]
Date DaysSince1970 I
4 2015-12-02 16771 4
1 2016-01-05 16805 1
2 2016-03-04 16864 2
> ds[isLastInRun(format(ds$Date, "%Y-%m")),]
Date DaysSince1970 I
6 2015-12-21 16790 6
1 2016-01-05 16805 1
3 2016-03-30 16890 3
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Thu, Jul 14, 2016 at 8:26 AM, Mehta, Gaurang <
gaurang.me...@royallondon.com> wrote:
> Hi Jeff,
> I would say my problem is what you described in 2 below. My data is as
> follows:
> Date UC11 UC12 UC13
> 02/01/1997 1 2 0
> 03/01/1997 5 6 3
> 06/01/1997 5 4 6
> 07/01/1997 6 4 3
> 08/01/1997 6 5 5
> 09/01/1997 7 6 8
> 10/01/1997 8 5 5
> 13/01/1997 8 6 5
> 14/01/1997 7 4 4
> 15/01/1997 6 3 3
> 16/01/1997 8 5 5
> 17/01/1997 6 4 3
> 20/01/1997 5 4 2
> 21/01/1997 7 5 5
> 22/01/1997 16 12 12
> 23/01/1997 5 3 4
> 24/01/1997 5 2 2
> 27/01/1997 8 4 5
> 28/01/1997 7 5 9
> 29/01/1997 4 4 4
> 30/01/1997 4 4 6
> 31/01/1997 9 7 8
> 03/02/1997 9 6 8
>
>
> I want to select the data on the first date it can be 1st , 2nd or 3rd or
> any and last date it can be 31st, 30th and /or29th. I don’t need time.
> It would be great if you could help.
> Regards,
> Gaurang Mehta
>
>
>
> -----Original Message-----
> From: Jeff Newmiller [mailto:jdnew...@dcn.davis.ca.us]
> Sent: 14 July 2016 16:03
> To: Mehta, Gaurang; R-help Mailing List
> Subject: Re: [R] Selecting 1st and last dates from a set of dates
>
> I suspect the answer to your question (is there a function...) is almost
> certainly yes, but your question is too vague to be sure.
>
> 1) Data frames and matrices are different in important ways... it is
> highly unlikely that matrices would be appropriate for date data.
>
> 2) Do you mean "select records with earliest date in each month" or
> "select records whose day of month is 1"? If you need to work with time of
> day along with date then the solution will be different than if you are
> working with date only.
>
> 3) Have you converted your dates to Date or POSIXct or chron already?
> Which?
>
> 4) There are a lot of useful functions in base R [1][2], as well as
> contributed packages such as chron and lubridate.
>
> A reproducible example [3] is the standard way to communicate what problem
> you actually have. In particular, including the output of dput for a
> representative sample of data is a key element of that example.
>
> [1] ?DateTimeClasses
> [2] R News 4/1 p29
> [3]
> http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example
> --
> Sent from my phone. Please excuse my brevity.
>
> On July 14, 2016 5:44:52 AM PDT, "Mehta, Gaurang" <
> gaurang.me...@royallondon.com> wrote:
> >Hi Team,
> >I am struggling to select the first date and last date of the month
> >where there is data in a dataframe/matrix.
> >Is there any r function that can help to easily select data on the
> >first and last day of the month from the given set of dates and values.
> >Thanks for the help in advance.
> >Regards,
> >Gaurang
> >
> >
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