On 2012-10-11 12:48, bibek sharma wrote:
Hello R help, I have a question similar to what is posted by someone before. my problem is that Instead of last assessment, I want to choose last two.I have a data set with several time assessments for each participant. I want to select the last assessment for each participant. My dataset looks like this: ID week outcome 1 2 14 1 4 28 1 6 42 4 2 14 4 6 46 4 9 64 4 9 71 4 12 85 9 2 14 9 4 28 9 6 51 9 9 66 9 12 84 Here is one solution for choosing last assessment do.call("rbind", by(df, INDICES=df$ID, FUN=function(DF) DF[which.max(DF$week), ])) ID week outcome 1 1 6 42 4 4 12 85 9 9 12 84
With the plyr package: library(plyr) ddply(df, .(ID), function(x) tail(x, 2)) or, slightly simpler: ddply(df, .(ID), tail, 2) Peter Ehlers ______________________________________________ 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.
