May I know how to formluate the rate equarion with VENSIM built-in functions for this DYNAMO exponential function EXP ?
e.g. Birth growth at a rate of 3% since year 2015 till now for initial population 1,000 people (GROWTHN=1000)
in DYNAMO , it would be like
GROWTH.KL = GROWTHN * EXP(0.03(TIME.K, 2015)
Thank you.
how to convert EXP dynamo to vensim
Re: how to convert EXP dynamo to vensim
It appears that some punctuation is missing or incorrect in that equation.
I would expect the true meaning to be something like:
Growth = GrowthN * EXP( 0.03 * (Time-2015) )
Also, embedding numbers in the equation is generally bad practice. For dimensional consistency and parameter testing, this should be rewritten as:
Growth = GrowthN * EXP( Growth Rate * (Time-Ref Year) ) ~ dmnl
GrowthN = ... ~ dmnl
Growth Rate = .03 ~ fraction/year
Ref Year = 2015 ~ year
"Growth" isn't a great variable name, so it would be nice to replace it with something more descriptive.
I would expect the true meaning to be something like:
Growth = GrowthN * EXP( 0.03 * (Time-2015) )
Also, embedding numbers in the equation is generally bad practice. For dimensional consistency and parameter testing, this should be rewritten as:
Growth = GrowthN * EXP( Growth Rate * (Time-Ref Year) ) ~ dmnl
GrowthN = ... ~ dmnl
Growth Rate = .03 ~ fraction/year
Ref Year = 2015 ~ year
"Growth" isn't a great variable name, so it would be nice to replace it with something more descriptive.
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