ivo welch wrote: > quizz---what does this produce? > > d=data.frame( a=1:1000, b=2001:3000, z= 5001:6000 ) > attach(d); c <- (a+b)>25; detach(d) > d= subset(d, TRUE, select=c( a, b, c )) > > yes, I know I have made a mistake, in that the code does not do what I > presumably would have wanted. What exactly did you want?