1 M: matrix([1,2,3,4],[1,2,3,2],[1,2,3,4],[1,2,3,3])$
2 f(x,y) := float('M [round(x), round(y)])$
3 plot3d (f(x,y), [x,1,4], [y,1,4], [grid,3,3], nolegend,
4 [pdf_file,"./plotting25.pdf"]);
5 plot3d (f(x,y), [x,1,4], [y,1,4], [grid,3,3], nolegend,
6 [png_file,"./plotting25.png"]);
