Rui, Thank You! the second one gave me NULL. dat$z2 <- unlist(tapply(dat$y1, dat$x1, function(y) y - y[1]))
dat$z2 NULL On Wed, Oct 12, 2016 at 3:34 PM, Rui Barradas <ruipbarra...@sapo.pt> wrote: > Hello, > > Seems simple: > > > # 1) > dat$x1 <- cumsum(dat$flag == "S") > > # 2) > dat$z2 <- unlist(tapply(dat$y1, dat$x1, function(y) y - y[1])) > > Hope this helps, > > Rui Barradas > > > Em 12-10-2016 21:15, Val escreveu: >> >> Hi all, >> >> I have a data set like >> dat<-read.table(text=" y1, flag >> 39958,S >> 40058,R >> 40105,X >> 40294,H >> 40332,S >> 40471,R >> 40493,R >> 40533,X >> 40718,H >> 40771,S >> 40829,R >> 40892,X >> 41056,H >> 41110,S >> 41160,R >> 41222,R >> 41250,R >> 41289,R >> 41324,X >> 41355,R >> 41415,X >> 41562,X >> 41562,H >> 41586,S >> ",sep=",",header=TRUE) >> >> First sort the data by y1. >> Then >> I want to create two columns . >> 1. the first new column is (x1): if flag is "S" then x1=1 and >> assign the following/subsequent rows 1 as well. When we reach to >> the next "S" then x1=2 and the subsequent rows will be assigned to >> 2. >> >> 2. the second variable (z2). Within each x1 find the difference >> between the first y1 and subsequent y1 values >> >> Example for the first few rows >> y1, flag, x1, z2 >> 39958, S, 1, 0 z2 is calculated as z2=(39958, 39958) >> 40058, R, 1, 100 z2 is calculated as z2=(40058, 39958) >> 40105, X, 1, 147 z2 is calculated as z2=(40105, 39958) >> 40294, H, 1, 336 z2 is calculated as z2=(40294, 39958) >> 40332, S, 2, 0 z2 is calculated as z2=(40332, 40332) >> etc >> >> Here is the complete output for the sample data >> 39958,S,1,0 >> 40058,R,1,100 >> 40105,X,1,147 >> 40294,H,1,336 >> 40332,S,2,0 >> 40471,R,2,139 >> 40493,R,2,161 >> 40533,X,2,201 >> 40718,H,2,386 >> 40771,S,3,0 >> 40829,R,3,58 >> 40892,X,3,121 >> 41056,H,3,285 >> 41110,S,4,0 >> 41160,R,4,50 >> 41222,R,4,112 >> 41250,R,4,140 >> 41289,R,4,179 >> 41324,X,4,214 >> 41355,R,4,245 >> 41415,X,4,305 >> 41562,X,4,452 >> 41562,H,4,452 >> 41586,S,5,0 >> >> Val >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> 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 -- To UNSUBSCRIBE and more, see 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.
