This is an openscad library to create 2d representations of equations (cartesian, polar, or parametric). You can export the graph to dxf or extrude it directly to make interesting objects like an ellipsoid. It's incredibly ineffecient and slow (can't really be helped, it is due to openscad limitations) and a little buggy still (probably my fault), but it mostly works. Enjoy!
Maybe if I can wrap my head around polyhedrons in openscad I will extend this to 3d functions. :)
function f(x) = ... // for a cartesian equation
function r(theta) = ... // for a polar equation
function x(t) = ... // and
function y(t) = ... // for a parametric equation
// param (optional) [lower bound, upper bound]
// param (optional) thickness of the line, without thickness it would be 1d!
// param (optional) number of polygons to draw (resolution)
// param (optional) polar=true or parametric=true, defaults to cartesian
2dgraph([-10, 10], 2, $fn=100);