@meso A plotted curve is a result of an equation in 2D or 3D space and of the points on the x or y axis you plug into the equation.

Of course the elliptic curves I was talking about in relation to Diffie-Hellman are standardized (usually Curve25519; If you look at the Matlab, you can see that I stole the equation for that, because I thought it would plot into something nice to look at. But it just looks like a parabola).