This example uses the techniques described in previous posts to draw level curves for functions of two variables z = F(x, y). The following posts describe the methods used by this example.

This example uses the same techniques to plot level curves. For a function z = F(x, y), the program simply plots the function F(x, y) – z = 0 for different z values. This example makes curves red when z < 0, blue when z > 0, and black when z = 0.

Note that this technique is non-analytic, so you don’t need to understand the shape of the function, find partial derivatives for it, etc. That makes it easy to use and apply to many kinds of functions, although you may miss special features of a function if you don’t understand its behavior. For example, if you plot level curves for z = 0, 1, 2, 3, 4, and 5 might miss interesting features if they occur when z = -1 or z = 2.5.

See the previous examples and download the code for the details.