Hi colleagues,
I request your assistance in modeling sigmoid behavior in an accumulated variable (a stock variable without outflows).
I need to model an accumulated variable with sigmoid behavior to incorporate it into a model that dynamically emulates its maximum.
I searched the forum for previous posts, but I didn't find a post that could help me solve the problem.
Thank you very much!
Help with a sigmoidal behaviour in a stock variable
Re: Help with a sigmoidal behaviour in a stock variable
Sounds like what you want is a logistic growth model. The model here https://vensim.com/vensim-video-library ... ith_Vensim has a variant of that near the 1hr mark, particularly if you make the product lifetime very long so that there's effectively no outflow from customers.
The general form is:
growth rate = max growth rate * (1-stock/ref stock) ~ fraction/time
stock = INTEG( growth, initial stock ) ~ stuff
growth = stock * growth rate ~ stuff/time
The general form is:
growth rate = max growth rate * (1-stock/ref stock) ~ fraction/time
stock = INTEG( growth, initial stock ) ~ stuff
growth = stock * growth rate ~ stuff/time
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Re: Help with a sigmoidal behaviour in a stock variable
There might be a molecule that does what you need (Tools->Molecules). There is a category titled "Close gap", maybe one of those?
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http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
Re: Help with a sigmoidal behaviour in a stock variable
Thank you @tomfid and @Administrator your advice really helped me.
The "smoothed quantity" molecule is very useful for my model! Also, the video library helps me in the understanding of the modeling process.
The "smoothed quantity" molecule is very useful for my model! Also, the video library helps me in the understanding of the modeling process.