xy <- expand.grid(seq(0,1,by=0.1),seq(0,1,by=0.1)) f5 <- 0.5 + 2.0*xy[,1] - 1.5*xy[,2] wireframe(f5~xy[,1]*xy[,2], screen = list(x = -90, y = 60), distance = .5, scales = list(arrows = FALSE), zlab="", main=expression('EY=0.5+2X'[1]-'1.5X'[2]), xlab=expression("X"[1]), ylab=expression("X"[2]))