How I can obtain graphics for response surface design, basing on data: x: 0.25, 1, 4, 10, 20. y: 0, 0.5, 1 z1 (for y = 0): 45, 35, 25, 15, 10. z2 (for y = 0.5): 50, 45, 36, 21, 17. z3 (for y = 1): 37, 34, 22, 17, 11? z-values should be scaled in colour (e. g. from red to blue). I consider to use packages "rsm" and "graphics" (with "grDevices"). I suggest to use Box-Behnken design in "rsm" and filled.contour in "graphics". However, I do not know how I can combain these two opportunities. I am not familiar in response surface analysis, and able to be wrong in the selection of the model. Thank you for any reply. With regard, Dmitry.