metabolite file

This function produces a pie chart that shows essentially how linear a subsystem is. It looks at all the metabolites contained in a particular subsystem. For each of these metabolites, the function looks at how many of the 7440 rxns contain it. Then the number of reactions for each metabolite is split into 4 (somewhat arbitrary) categories. So in the pie chart, a category of "<=5 rxns 17%" means 17% of the metabolites in the subsystem are found in less than 5 reactions.