GeoGebra doesn't do contour plots (as far as I can work out), but it is a great piece of free graphing software.
I wrote an introductory review here: GeoGebra math software - a review, which contains relevant links. I wrote an earlier article Graphs using free math software which you may find interesting.Īlso, GeoGebra remains a favorite.
You may also need to download other required software (like Ghostscipt, which is an interpreter for PostScript and PDF). That is, you need to write your script in a text editor to get your graphs - there is no simple graphical user interface.
GLE can output to PDF, EPS, PS, SVG (scalable vector graphics), PNG and JPEG (for the Web). It can also do 3-D plots, fractals and electronic circuit diagrams. The good: It produces nice clean graphs and can handle a wide range of function types, including vector fields, split functions and statistics. Graphics Layout Engine is an open source offering, but not for the faint-hearted. The bad: Windows only (no Mac or Linux versions). The good: Winplot can plot a large range of function types, including explicit and implicit functions, vector fields, parametric equations and 3-D plots, as well as contour plots as you can see below. Winplot by Richard Parris (deceased) of Philips Exeter Academy has been around for many years. The first is the easiest to use and most appropriate for you. The learners are the ones who will stay young. I'm impressed with the number of retirees who maintain an interest in mathematics. I received a delightful mail from Morgan, a 95-year old reader.