ddply(z, .(groupId,location),function(d)with(d, c(startLoc=Pos[1],endLoc=Pos[length(Pos)], peakValue=max(sumoo),other=map[1]))) startLoc=Pos[1],endLoc=Pos[length(Pos)], peakValue=max(sumoo),====numeric value other=map[1]===charactor value as a result: c(startLoc=Pos[1],endLoc=Pos[length(Pos)], peakValue=max(sumoo),other=map[1]) ===convert all values to charactor. my question, How can i separate the numeric and charactor values from above statement? Thanks, -- View this message in context: http://r.789695.n4.nabble.com/ddply-error-tp2304485p2304485.html Sent from the R help mailing list archive at Nabble.com.