Issue with Monte Carlo Sensitivity Analysis in Vensim

[VirginiaRosa]

Dear Vensim Forum Members,

I am reaching out to seek assistance with a problem I encountered while conducting a Monte Carlo sensitivity analysis on my model.

To provide some context, I have constructed a deterministic model aimed at analyzing water demand within a specific area. To introduce stochasticity and uncertainty into the simulation, I have defined some input variables to follow probability distributions using random functions (I calculated the parameter of the random function with R and then added it to my Vensim model). To observe how the values of these random variables fluctuate across different simulations, I opted for a multivariate sensitivity analysis.

Specifically, I selected one of my random variables ('Population', described through a random Weibull) and asked Vensim to perform a sensitivity analysis with a random Weibull distribution. I started with a low number of simulations, precisely 2, focusing on just one variable from the list ('drinking water demand'). However, upon running the analysis, Vensim returned an error message which I have included below. I am struggling to identify the root cause of this issue. Could it be related to the fact that the variable I selected for sensitivity analysis is already a random function? Or perhaps it is a matter of model complexity? Could it have something to do with the fact that my model works with different subscripts?

I would greatly appreciate any insights or guidance you can offer to help me troubleshoot and resolve this issue. Thank you very much for your time and assistance.

Best regards,
Virginia

[Administrator]

Can you upload the model and associated files so we can try and run the same thing?

What version of Vensim are you using?

[VirginiaRosa]

Could I send the model internally? I cannot show it publicly. I have restrictions on this

[Administrator]

Please do, vensim@vensim.com. Please ensure you include your licence details.