Hi, In addition to merge(), you can also use join() dat1<-read.table(text=" tdate event_tim transaction 1/10/2012 2 14 1/10/2012 4 28 1/10/2012 6 42 1/10/2012 8 14 2/10/2012 6 46 2/10/2012 9 64 2/10/2012 8 71 3/10/2012 3 85 3/10/2012 1 14 3/10/2012 4 28 9/10/2012 5 51 9/10/2012 9 66 9/20/2012 12 84 ",sep="",header=TRUE,stringsAsFactors=FALSE) dat2<-dat1[with(dat1,order(tdate,event_tim)),] aggres<-aggregate(dat2[,-1],by=list(tdate=dat2$tdate),tail,1) aggres$last_trans<-"Y" library(plyr)
join(dat2,aggres,by=intersect(names(dat2),names(aggres)),type="full") # tdate event_tim transaction last_trans #1 1/10/2012 2 14 <NA> #2 1/10/2012 4 28 <NA> #3 1/10/2012 6 42 <NA> #4 1/10/2012 8 14 Y #5 2/10/2012 6 46 <NA> #6 2/10/2012 8 71 <NA> #7 2/10/2012 9 64 Y #8 3/10/2012 1 14 <NA> #9 3/10/2012 3 85 <NA> #10 3/10/2012 4 28 Y #11 9/10/2012 5 51 <NA> #12 9/10/2012 9 66 Y #13 9/20/2012 12 84 Y A.K. ----- Original Message ----- From: ramoss <ramine.mossad...@finra.org> To: r-help@r-project.org Cc: Sent: Friday, October 19, 2012 1:51 PM 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@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@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.
