Dear all, I have carried out a pairwise comparison study that I want to analyze using the BradleyTerry package to establish a rank order of my stimuli. However, BT does not handle ties between stimuli, so I need to find those in my data before I can use that model.
The code below goes from the format of my result file(s) to a data frame suitable for BT, but as you can see, there are some ties. I need to find the rows with identical (but swapped) winner and loser and with the same frequency. How can I accomplish that using the R-way (not looping through the entire thing; in reality, I have approx 40 stimuli with around 180 observations of an odd 40 subjects)? # $lp was left picture; $rp, right one; $wr was the winner/chosen one by subject. dat <- data.frame(subjno=gl(4,3), lp=factor(c(1,3,2,2,3,1,3,1,2,1,2,3), labels=c('a','b','c')), rp=factor(c(2,1,3,3,1,2,1,2,3,3,1,2), labels=c('a', 'b', 'c')), wr=factor(c(1,1,2,1,2,2,1,1,2,2,1,2), labels=c('lp', 'rp'))) dat.lp <- subset(dat, wr=='lp') dat.rp <- subset(dat, wr=='rp') names(dat.rp)[c(2,3)] <- c('loser', 'winner') names(dat.lp)[c(2,3)] <- c('winner', 'loser') (dat <- with(merge(dat.lp, dat.rp, all=TRUE), data.frame(table(winner,loser)))) Thank you for your help! ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html