Hi, May be this helps: res1<-df1[with(df1,unlist(tapply(var,list(subid),FUN=function(x) c(FALSE,diff(x)!=0)),use.names=FALSE)),] res1 # subid year var #3 36 2003 3 #7 47 2001 3 #9 47 2005 1 #10 47 2007 3 #or library(plyr) subset(ddply(df1,.(subid),mutate,delta=c(FALSE,diff(var)!=0)),delta)[,-4] # subid year var #3 36 2003 3 #7 47 2001 3 #9 47 2005 1 #10 47 2007 3 A.K.
I need to output a dataframe whenever var changes a value. df1 <- data.frame(subid=rep(c(36,47),each=5),year=rep(seq(1999,2007,2),2),var=c(1,1,3,3,3,1,3,3,1,3)) subid year var 1 36 1999 1 2 36 2001 1 3 36 2003 3 4 36 2005 3 5 36 2007 3 6 47 1999 1 7 47 2001 3 8 47 2003 3 9 47 2005 1 10 47 2007 3 > I need: 36 2003 3 47 2001 3 47 2005 1 47 2007 3 I am trying to use ddply over subid and use the diff function, but it is not working quiet right. > dd <- ddply(df1,.(subid),summarize,delta=diff(var) != 0) > dd subid delta 1 36 FALSE 2 36 TRUE 3 36 FALSE 4 36 FALSE 5 47 TRUE 6 47 FALSE 7 47 TRUE 8 47 TRUE I would appreciate any help on this. Thank You! -ST ______________________________________________ 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.
