> > Oh! because I would like to plot an implicit function R(x,y) = 0, > > addplot3 seems to plot the threedimensional visualization. > > I don't think either tikz or gnuplot support such functional plot. Yes, addplot3 is a 3D visualization, given x,y. Hmmm, I am not a friend to implicit function. But my thinking (maybe totally wrong) is displayed below. since y is supposed to be a function of x, i.e., y=f(x), is it possible to use derivative technique to find analytic function of x, then plot f(x) using addplot. If singularity is/are encountered, just avoid plotting it/them. If not applicable, here is a website for related problem. Hoping it will help. http://pbelmans.wordpress.com/2010/11/11/howto-draw-algebraic-curves-using-pgftikz/ Good luck