Sage is a free open source mathematical software package that can do lots of things. In particular, it can handle graphs. Here is an example of how to create and plot a graph in Sage.
There are lots of commands that you can apply to a graph. For example, here are some commands to try:
G.complement()G.adjacency_matrix()G.degree_sequence()Just copy and paste these commands into the box above. You should also try creating different graphs and seeing how the Graph() function works.
Here are some more examples using Sage to compute different things.