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Translation of Urban Dynamics Model

Posted: Wed Sep 20, 2000 6:00 pm
by Bill Braun
Ive "translated" Jay Forresters Urban Dynamics model (Appendix A from
Urban Dynamics) into Powersim. The output of the model is close to the
tables in Chapter 3 (Growth and Stagnation, which I have taken to be
outputs from the baseline model). However, the output values are not exact.

I suspect that the fault lies in the manner in which I am treating the
integration takes place in the DYNAMO equations for the "multiplier
perceived" levels and which are handled by Powersim as first-order
information delay functions, or so I think.

Im also suspicious of the way Ive "translated" the integration equations
that contain LOG functions in the DYNAMO equations.

Has anyone constructed Urban Dynamics in Powersim and had it perform the
same way the DYNAMO model performs? Could I compare equations in your model?

Thank you,

Bill Braun

P.S. Anyone is welcome to the Powersim model that Ive translated (as it
now exists). It is available at

Once I make the corrections to it, Ill post a follow-up and the corrected
version will also be available.