Vensim and Digest

[karankhosla]

Greetings,

I can't seem to get my Vensim based (Forrester's) market growth model to work in Digest. Any suggestions?

Karan

[Administrator]

Is Digest an application?

[karankhosla]

Hi! Yes, It's a fantastic little tool to analyze SD model behavior and identify influential system structures (loop dominance etc)

The application is available on George Richardson's website, so I presume it's open source (scroll to the bottom):

http://www.albany.edu/cpr/sdgroup/pad824/schedule.html

Here's a paper by Richardson, Andersen and Mojtahedzadeh

http://www.systemdynamics.org/conferenc ... RS/W11.pdf

It works with some ".mdls" and not with others.

Check it out!

Best,

Karan

[Administrator]

This is just a guess as I've never seen Digest before today. I'd assume that there is a function in your model that Digest doesn't know about. And the error message doesn't really give any clue what this could be.

[tomfid]

I'd just run through the text and look for unusual functions, though it could be something as simple as an IF THEN ELSE. Any discrete behavior will wreak havoc on the linearlization of the model, I'd guess.

Also look for any variable names that incorporate special characters and therefore require " " - those might also fool the parser.

Tom

[karankhosla]

Thank you both very much!

[LAUJJL]

Hi everybody

I have in the past downloaded too Digest from the same Rchardson's learning place.

But I never tried to use it, as it seemed to me a bit complicate.

Another problem is that tools centered on loops analysis work only as long as there are not too many of them to analyze which happens very quickly as one develops a model.

I thought too that before relying to such tools, I had better first master all the tools available in Vensim a task that is far from being finished.

Digest seems to work well with Vensim. Are there any people in the Forum (administrators for example) using Digest or eigenvalues or Ford's method (loops centered methods)?

Regards.

JJ