I'm trying to simulate an stochastic SIR model following the Gillespie algorithm, as described here .
When trying to update each process' probabilities, it looks like Maple is not updating their values. Although each element of the lists S, I and R is updated the ai lists are not updated.
For example, for a given index i
takes the same value for every i, regardless of the value of S[i].
Can anybody tell why this is happening or what's wrong with the worksheet? This is the attempt: MaplePrimes_SIR_model_simulation_Gillespie_algorithm.mw
On the other hand, I tried making things more clear through a couple of procedures. However, when it comes to the point where a random number with an exponential distirbution is computed:
Rexp := RandomVariable(Exponential(mu)):
it looks like Maple is unable to evaluate mu. But having a look at the Variables explorer, it has a defined value, indeed.
So what's wrong in the worksheet? Thi is the attempt: MaplePrimes_SIR_model_simulation_Gillespie_algorithm.mw