title: How can I plot a function with two variables in Octave or Matlab?
body: <p>I want to use Octave to plot fairly simple functions with two variables like: f(x,y) = x^2 + 3y .  It is very easy to plot single variable functions, but I am having a lot of trouble finding out how to do two variable functions.  Does anyone know the best way of doing this?  </p>