> Finally I would like to have a data.frame t2 which only contains the > entries of the last measurements. >
You could also use aggregate to get the max year per plate then join that back to the original dataframe using merge on year and plate (common columns in both dataframes). x<-data.frame(id=(1:8), plate=c(15,15,15,20,20,33,43,43), year=c(2004,2005,2006,2004,2005,2004,2005,2006), height=c(0.40,0.43,0.44,0.90,0.94,0.15,0.30,0.38)) merge(x, aggregate(list(year=x$year), list(plate=x$plate), max)) plate year id height 1 15 2006 3 0.44 2 20 2005 5 0.94 3 33 2004 6 0.15 4 43 2006 8 0.38 ______________________________________________ [email protected] 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.
