On Sun, Aug 16, 2009 at 9:19 PM, malcolm Crouch<malcolm.croucher at gmail.com> wrote: >> plot(V6,V5, col="red") > or >> plot(V6,V5) It seems that V5 and V6 are column names in your data matrix. If your matrix is called data, you should use plot(x$V6,x$V5,col="red") instead. Best, Michael -- Michael Knudsen micknudsen at gmail.com http://lifeofknudsen.blogspot.com/