how to program a curve tracer of mathematical functions

[himself15]

hello
I've been looking for a way to do this for quiet sometime now. well the Idea is (it's not so new!!) that the user gets to enter a mathematical function such as (3x²+ 2x)/(3x + 1) for example. now let me worry about the processing of the function, what I'm asking about is, one I get a table with the (X,Y) coordinates of the points, how can I actually draw the curve and end up with something like this
http://www.mathe-fa.de/fr.plot.png?u...77140.99594621
as I said I've been asking around for some help, and the thing is that everybody just says "you can use the GD library" well I've been through it and I still can't see how I'm going to get even the reference (repère orthonormé). others said that this can be done with some javascripts. would somebody please tell me what to do, or at least name some functions that can actually help
regards

[Dormilich]

if you’d use GD, you need to draw the image piece by piece yourself (e.g. through imageline()), though the overall process also includes creating the image resource and some more steps.

In JS it is a little bit simpler, but still you need to (manually) draw the lines on the canvas.