On Thu, Apr 7, 2011 at 2:29 PM, Rita Carreira <ritacarre...@hotmail.com> wrote: > > Hello everyone! > I have a data frame of 136 variables with 270 observations. I would like to > create a new data frame such that each element of that data frame contains > the maximum value of the 6 prior lags of the initial data frame. So for > example, if my original data frame, A, were > A1=c(7.72, 7.94, 7.56, 7.54, 0.93, 0.59, 7.21, 8.00, 7.19, 7.57)A2=c(4.27, > 3.70, 3.80, 3.67, 3.83, 3.95, 4.02, 2.06, 3.28, 2.17)A3=c(4.16, 2.91, 3.89, > 3.73, 4.00, 3.81, 3.86, 1.88, 3.74, 3.75)A4=c(3.56, 3.27, 3.42, 3.32, 3.48, > 3.54, 3.60, 2.04, 3.38, 3.37)A5=c(8.24, 8.67, 8.49, 0.00, 9.39, 0.00, 8.49, > 8.94, 0.00, 0.00)A6=c(4.28, 4.18, 4.20, 4.14, 4.40, 4.20, 4.20, 4.15, 4.17, > 4.16) > A <- cbind(A1, A2, A3, A4, A5, A6) > My new data frame, Amax, where each element is amax(i,j)=max[a(i-1,j), > a(i-2,j), a(i-3,j), a(i-4,j), a(1-5,j), a(i-6,j)] would be:NA NA NA NA > NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA > NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA > 7.94 > 4.27 > 4.16 > 3.56 > 9.39 > 4.40 7.94 > 4.02 > 4.00 > 3.60 > 9.39 > 4.40 8.00 > 4.02 > 4.00 > 3.60 > 9.39 > 4.40 8.00 > 4.02 > 4.00 > 3.60 > 9.39 > 4.40 8.00 > 4.02 > 4.00 > 3.60 > 9.39 > 4.40 > So the question is: what is the most efficient way of doing this in R? > Thanks!Rita ________________________________________ "If you think education > is expensive, try ignorance"--Derek Bok
See rollmax in the zoo package and see ?rollmax for the various options. e.g. using the built in BOD data frame: > library(zoo) > as.data.frame(rollmax(BOD, 3, na.pad = TRUE, align = "right")) Time demand 1 NA NA 2 NA NA 3 3 19.0 4 4 19.0 5 5 19.0 6 7 19.8 -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.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.
