How to model an overshoot and collapse graph?

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zetagman
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How to model an overshoot and collapse graph?

Post by zetagman »

I am trying to model my stockflow diagram to mimic the shape of this graph: http://imgur.com/HH0vcgH

However I do not know how to execute it given my current stock flow diagram, with my rates, auxiliary variables and level variables.
The topic is about the rise and fall on the number of dengue cases, and it rises usually during rainy season (Start at week 21) and collapses at the end of it (ends around at 49).
The X-axis of the graph is in terms of morbidity week but it can also be turned into months (1 month = 4 weeks).

Some notes/assumptions:
The system only considers a place that has wet and dry seasons
The number of people vaccinated variable should ideally reduce the height of the curve on the number of people infected. The vaccine is said to prevent 8 out of 10 cases of dengue.
Mosquitoes can be infected with the dengue virus (if it feeds on a person that already has the virus) or not. (My arrows may not be complete and should be reconfigured)
Climate influences the breeding behavior of mosquitoes and where they frequent (ex: During rainy season the mosquitoes go out to breed in open spaces while in dry season, the mosquitoes go to areas with water, which are much less than during the rainy season)
Mosquito lifespan is just a constant number of how long the mosquito usually lives

Feel free to add/remove/change variables in my stock flow diagram to make it possible, I will try to make sense of the recommendations.
Attachments
Stockflow Diagram.mdl
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Re: How to model an overshoot and collapse graph?

Post by Administrator »

The model does not simulate, there are no equations for any of the variables.
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391

Units are important!
http://www.bbc.co.uk/news/magazine-27509559
Edythe
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Re: How to model an overshoot and collapse graph?

Post by Edythe »

In general, an effective approach to modeling is to start with a very small set of relationships. Determine the functions that represent the limit set and ensure that the behavior is as you expect before adding more parts. That way, if/when the behavior is not correct, you know that the error must be in the last part you added. Based on the lack of equations in hte model attached here, I assumed you took a different approach.

The resource below might be helpful.

https://ocw.mit.edu/courses/sloan-schoo ... neric3.pdf
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