Thanks for the answer; I see that col=c("blue","red")[inv$c+1] creates a vector of "red" and "blue" associated with the binnary c. But still I got everything red. -- View this message in context: http://r.789695.n4.nabble.com/Simple-question-about-symbols-tp3461676p3462013.html Sent from the R help mailing list archive at Nabble.com.