Hi David, [This is a late reaction to a question I posted some time ago...]
thanks to your suggestion I found another solution which does carry out the random assignment. df[,2] <- as.numeric( rank(df[,2],ties.method="random") > length(df[,2])/2 ) Maybe this will be of interest to the R-List (and hopefully this is a correct solution) ... All the best Alain > David Winsemius <dwinsem...@comcast.net> hat am 7. Mai 2013 um 19:00 > geschrieben: > > > > On May 7, 2013, at 9:20 AM, D. Alain wrote: > > > Dear R-List, > > > > I would like to recode categorial variables into binary data, so that all > > values above median are coded 1 and all values below 0, separating each var > > into two equally large groups (e.g. good performers = 0 vs. bad performers > > =1). > > > > I have not succeeded so far in finding a nice solution to do that in R. I > > thought there might be a better way than ordering each column and recoding > > the first 50% into 0 and the second into 1. If I use ifelse I have a problem > > with cases that share the same rank being all median. > > > > e.g. > > df<-as.data.frame(cbind(snr=c(1,2,3,4,5,6,7,8,9,10),k1=c(1,1,4,2,3,2,2,5,2,2),k2=c(1,2,3,2,1,2,1,3,3,2),result=c(4,3,5,4,2,6,4,4,2,3))) > > First off, stop using cbind() when it is not needed. You will not see the > reason when the columns are all numeric but you will start experiencing pain > and puzzlement when the arguments are of mixed classes. The data.frame > function will do what you want. (Where do people pick up this practice > anyway?) > > > > df[,2] <- as.numeric( order(df[,2]) >= length(df[,2])/2 ) > > > > > > > > now I want to recode k1 and k2 so that I have half of the values recoded 0 > > and half recoded 1, split around the median point. The median of k1 is 2 > > which would lead to unequal groupsize if used 2 as cutoff, so all values > > k1=2 should be recoded 1 or 0 randomly until both categories have the same > > length. > > > > something like > > > > df.rec<-as.data.frame(cbind(snr=c(1,2,3,4,5,6,7,8,9,10),k1=c(0,0,1,0,1,1,0,1,0,1),k2=c(0,1,1,0,0,1,0,1,1,0),result=c(4,3,5,4,2,6,4,4,2,3))) > > > > Can anyone help? > > > > Thank you in advance. > > > > Best wishes. > > Alain > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. > > David Winsemius > Alameda, CA, USA > [[alternative HTML version deleted]] ______________________________________________ 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.
