[R] Creating a new by variable in a dataframe

William Dunlap wdunlap at tibco.com
Sat Oct 20 19:53:23 CEST 2012


> d$flag2 <- unlist(lapply(unname(split(d[[3]], d$date), function(x)x==max(x))))
I'm sorry, I stuck in the unname() in the mail but did not run it - its closing
parenthesis should be after split's closing parenthisis, not at the end.

> d$flag2 <- unlist(lapply(unname(split(d[[3]], d$date)), function(x)x==max(x)))
> identical(d$flag , d$flag2)
[1] TRUE

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: arun [mailto:smartpink111 at yahoo.com]
> Sent: Saturday, October 20, 2012 9:29 AM
> To: William Dunlap
> Cc: R help; Flavio Barros; ramoss
> Subject: Re: [R] Creating a new by variable in a dataframe
> 
> HI Bill,
> 
> Thanks for the reply.
> It was unnecessarily complicated.
> d$flag<-unlist(lapply(split(d,d$date),function(x) x[3]==max(x[3])),use.names=FALSE)
> #or
> d$flag<-unlist(lapply(split(d,d$date),function(x) x[3]==max(x[3])))
> should have done the same job.
> str(d)
> #'data.frame':    10 obs. of  4 variables:
> # $ transaction: chr  "T01" "T02" "T03" "T04" ...
> # $ date       : Date, format: "2012-10-19" "2012-10-19" ...
> # $ time       : int  8 9 10 11 12 13 14 15 16 17
>  #$ flag       : logi  FALSE FALSE FALSE TRUE TRUE FALSE ...
> 
> I am getting error messages with:
> d$flag2 <- unlist(lapply(unname(split(d[[3]], d$date), function(x)x==max(x))))
> Error in match.fun(FUN) : argument "FUN" is missing, with no default
> 
> 
> A.K.
> 
> 
> 
> 
> 
> ----- Original Message -----
> From: William Dunlap <wdunlap at tibco.com>
> To: arun <smartpink111 at yahoo.com>; Flavio Barros <flaviomargarito at gmail.com>
> Cc: R help <r-help at r-project.org>; ramoss <ramine.mossadegh at finra.org>
> Sent: Saturday, October 20, 2012 12:04 PM
> Subject: RE: [R] Creating a new by variable in a dataframe
> 
> > d$flag<-unlist(rbind(lapply(split(d,d$date),function(x) x[3]==max(x[3]))))
> 
> I think that line is unnecessarily complicated. lapply() returns a list
> and rbind applied to one argument, L, mainly adds dimensions c(length(L),1)
> to it (it also changes its names to rownames).  unlist doesn't care about
> the dimensions, so you may as well leave out the rbind.  The only difference
> in the results with and without calling rbind is that the rbind version omits
> the names from flag.  Use the more direct unname() on split's output or
> unlists's output if that concerns you.
> 
> Also, if you are interested in saving time and memory when the input, d, is large,
> you will be better off applying split() to just the column of the data.frame
> that you want split instead of to the entire data.frame.
>    d$flag2 <- unlist(lapply(unname(split(d[[3]], d$date), function(x)x==max(x))))
> (I used d[[3]] instead of the more readable d$time to follow your original more closely.)
> 
> You ought to check that the data is sorted by date: otherwise these give the
> wrong answer.
> 
> What result do you want when there are several transactions at the last time
> in the day?
> 
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
> 
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> > Of arun
> > Sent: Friday, October 19, 2012 7:49 PM
> > To: Flavio Barros
> > Cc: R help; ramoss
> > Subject: Re: [R] Creating a new by variable in a dataframe
> >
> >
> >
> > HI,
> > Without using "ifelse()" on the same example dataset.
> > d <- data.frame(stringsAsFactors = FALSE, transaction = c("T01", "T02",
> > "T03", "T04", "T05", "T06", "T07", "T08", "T09", "T10"),date =
> > c("2012-10-19", "2012-10-19", "2012-10-19", "2012-10-19", "2012-10-22",
> > "2012-10-23", "2012-10-23", "2012-10-23", "2012-10-23", "2012-10-23"),time
> > = c("08:00", "09:00", "10:00", "11:00", "12:00", "13:00", "14:00", "15:00",
> > "16:00", "17:00"))
> >
> > d$date <- as.Date(d$date,format="%Y-%m-%d")
> > d$time<-strptime(d$time,format="%H:%M")$hour
> > d$flag<-unlist(rbind(lapply(split(d,d$date),function(x) x[3]==max(x[3]))))
> > d$datetime<-as.POSIXct(paste(d$date,d$time," "),format="%Y-%m-%d %H")
> > d1<-d[,c(1,5,4)]
> >  d1
> > #   transaction            datetime  flag
> > #1          T01 2012-10-19 08:00:00 FALSE
> > #2          T02 2012-10-19 09:00:00 FALSE
> > #3          T03 2012-10-19 10:00:00 FALSE
> > #4          T04 2012-10-19 11:00:00  TRUE
> > #5          T05 2012-10-22 12:00:00  TRUE
> > #6          T06 2012-10-23 13:00:00 FALSE
> > #7          T07 2012-10-23 14:00:00 FALSE
> > #8          T08 2012-10-23 15:00:00 FALSE
> > #9          T09 2012-10-23 16:00:00 FALSE
> > #10         T10 2012-10-23 17:00:00  TRUE
> >
> > str(d1)
> > #'data.frame':    10 obs. of  3 variables:
> > # $ transaction: chr  "T01" "T02" "T03" "T04" ...
> > # $ datetime   : POSIXct, format: "2012-10-19 08:00:00" "2012-10-19 09:00:00" ...
> > # $ flag       : logi  FALSE FALSE FALSE TRUE TRUE FALSE ...
> >
> > A.K.
> >
> >
> > ----- Original Message -----
> > From: Flavio Barros <flaviomargarito at gmail.com>
> > To: William Dunlap <wdunlap at tibco.com>
> > Cc: "r-help at r-project.org" <r-help at r-project.org>; ramoss
> > <ramine.mossadegh at finra.org>
> > Sent: Friday, October 19, 2012 4:24 PM
> > Subject: Re: [R] Creating a new by variable in a dataframe
> >
> > I think i have a better solution
> >
> > *## Example data.frame*
> > d <- data.frame(stringsAsFactors = FALSE, transaction = c("T01", "T02",
> > "T03", "T04", "T05", "T06", "T07", "T08", "T09", "T10"),date =
> > c("2012-10-19", "2012-10-19", "2012-10-19", "2012-10-19", "2012-10-22",
> > "2012-10-23", "2012-10-23", "2012-10-23", "2012-10-23", "2012-10-23"),time
> > = c("08:00", "09:00", "10:00", "11:00", "12:00", "13:00", "14:00", "15:00",
> > "16:00", "17:00"))
> >
> > *## As date tranfomation*
> > d$date <- as.Date(d$date)
> > d$time <- strptime(d$time, format='%H')
> >
> > library(reshape)
> >
> > *## Create factor to split the data*
> > fdate <- factor(format(d$date, '%D'))
> >
> > *## Create a list with logical TRUE when is the last transaction*
> > ex <- sapply(split(d, fdate), function(x)
> > ifelse(as.numeric(x[,'time'])==max(as.numeric(x[,'time'])),T,F))
> >
> > *## Coerce to logical vector*
> > flag <- unlist(rbind(ex))
> >
> > *## With reshape we have the transform function e can add the flag column *
> > d <- transform(d, flag = flag)
> >
> > On Fri, Oct 19, 2012 at 3:51 PM, William Dunlap <wdunlap at tibco.com> wrote:
> >
> > > Suppose your data frame is
> > > d <- data.frame(
> > >      stringsAsFactors = FALSE,
> > >      transaction = c("T01", "T02", "T03", "T04", "T05", "T06",
> > >         "T07", "T08", "T09", "T10"),
> > >      date = c("2012-10-19", "2012-10-19", "2012-10-19",
> > >         "2012-10-19", "2012-10-22", "2012-10-23",
> > >         "2012-10-23", "2012-10-23", "2012-10-23",
> > >         "2012-10-23"),
> > >      time = c("08:00", "09:00", "10:00", "11:00", "12:00",
> > >         "13:00", "14:00", "15:00", "16:00", "17:00"
> > >         ))
> > > (Convert the date and time to your favorite classes, it doesn't matter
> > > here.)
> > >
> > > A general way to say if an item is the last of its group is:
> > >   isLastInGroup <- function(...)  ave(logical(length(..1)), ...,
> > > FUN=function(x)seq_along(x)==length(x))
> > >   is_last_of_dayA <- with(d, isLastInGroup(date))
> > > If you know your data is sorted by date you could save a little time for
> > > large
> > > datasets by using
> > >   isLastInRun <- function(x) c(x[-1] != x[-length(x)], TRUE)
> > >   is_last_of_dayB <- isLastInRun(d$date)
> > > The above d is sorted by date so you get the same results for both:
> > >   > cbind(d, is_last_of_dayA, is_last_of_dayB)
> > >      transaction       date  time is_last_of_dayA is_last_of_dayB
> > >   1          T01 2012-10-19 08:00           FALSE           FALSE
> > >   2          T02 2012-10-19 09:00           FALSE           FALSE
> > >   3          T03 2012-10-19 10:00           FALSE           FALSE
> > >   4          T04 2012-10-19 11:00            TRUE            TRUE
> > >   5          T05 2012-10-22 12:00            TRUE            TRUE
> > >   6          T06 2012-10-23 13:00           FALSE           FALSE
> > >   7          T07 2012-10-23 14:00           FALSE           FALSE
> > >   8          T08 2012-10-23 15:00           FALSE           FALSE
> > >   9          T09 2012-10-23 16:00           FALSE           FALSE
> > >   10         T10 2012-10-23 17:00            TRUE            TRUE
> > >
> > >
> > > Bill Dunlap
> > > Spotfire, TIBCO Software
> > > wdunlap tibco.com
> > >
> > >
> > > > -----Original Message-----
> > > > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> > > On Behalf
> > > > Of ramoss
> > > > Sent: Friday, October 19, 2012 10:52 AM
> > > > To: r-help at r-project.org
> > > > Subject: [R] Creating a new by variable in a dataframe
> > > >
> > > > Hello,
> > > >
> > > > I have a dataframe w/ 3 variables of interest: transaction,date(tdate) &
> > > > time(event_tim).
> > > > How could I create a 4th variable (last_trans) that would flag the last
> > > > transaction of the day for each day?
> > > > In SAS I use:
> > > > proc sort data=all6;
> > > > by tdate event_tim;
> > > > run;
> > > >          /*Create last transaction flag per day*/
> > > > data all6;
> > > >   set all6;
> > > >   by tdate event_tim;
> > > >   last_trans=last.tdate;
> > > >
> > > > Thanks ahead for any suggestions.
> > > >
> > > >
> > > >
> > > > --
> > > > View this message in context:
> > > http://r.789695.n4.nabble.com/Creating-a-new-by-
> > > > variable-in-a-dataframe-tp4646782.html
> > > > Sent from the R help mailing list archive at Nabble.com.
> > > >
> > > > ______________________________________________
> > > > R-help at r-project.org mailing list
> > > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > > PLEASE do read the posting guide
> > > http://www.R-project.org/posting-guide.html
> > > > and provide commented, minimal, self-contained, reproducible code.
> > >
> > > ______________________________________________
> > > R-help at r-project.org mailing list
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide
> > > http://www.R-project.org/posting-guide.html
> > > and provide commented, minimal, self-contained, reproducible code.
> > >
> >
> >
> >
> > --
> > Att,
> >
> > Flávio Barros
> >
> >     [[alternative HTML version deleted]]
> >
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.




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