To see what model looks like when run click here
To create this model:
We are constructing a model which has a target to reach.
We'll call this the desired goal. The desired goal could be
in the form of a stock or a converter. In this case we are using
a converter. We have another converter which serves to
adjust the flow's rate at which we approach our target. For
example, let's say we have a population of 10 individuals of
an endangered specie. We want to have them reach a population
of 150 individuals. (Yeah, I know...this is extremely simplistic...
what do you want for free?)
To create the model:
- Select a stock, name it Population and give it the value 10
- Select a flow, make it an inflow (pointing into the stock), give it the name births.
- Connect the current stock (population) to the flow.
- Select a converter, call it targetpop, give it the value 150 and connect it to the flow.
- Select another converter, call it birth rate, give it the value .25 and connect it to the flow.
- Open the flow. The flow is equal to the resulst of the subtraction of the desired goal (targetpop) minus the current goal (Population) times the adjustment fraction (birth rate).
- Open the graph and graph both the desired goal and the current stock.