how to plot food web
 

Could somebody tell me how to plot food web in Matlab. For instance, we have 3 species , a,b and c. And we know a is resource and b is the resource-consumer and c is the top predator that eats b and a. I hope the figure look likes as follows: resource is denoted by a solid cycle with a number located in the center of the cycle and some color.

So throught this plot, I can see the relationship between different species and the number of species and some arrows.


Thanks very much