Ventana software support forum

Hi all,
as I cannot use any longer VENSIM DSS I'd like to know , in summary, what I'm going to lose If I use vensim PLE. Particularly on the number of equations and optimization functions. I know already that subscripts are not available within PLE.

Thanks
G

Hi JJ, I agree with you, probably it's not correct to say "we want to target SD to business people". And I agree that type 1 managers will not be willing to invest time in studying and trying new techniques and approaches. Probably the best target is a category of "visionary people&qu...

Hi Ralf, that's exactly what I have in mind. Every time I met a manager or an executive I try to describe what the methodology is and I lost them immediately. Also the potential benefits are quite obscure to them, because when they heard that there is modelling involved they close their ears.... I t...

Many thanks to everybody, I'll had a look at all the examples
!!
Hope to return the help back at some point in time!!

Ciao!

G

Hi JJ,
I'm on the simpler example on page 242 (The performance of a simple model) , the one prior to DMC example.
Attached the model in VENSIM

Thanks!!!
G

Hi all, I'm doing some exercise on optimization, particularly I'm working on the very simple example contained in Coyle's book. Basically the objective function for the optimization should be the difference between desired inventory and inventory and the parameters are 4 constants (time_to_correct_i...

Hi all,
thanks for the suggestions and hints. We'll simplify the model in order to reduce the simultaneity and correct all the unit of measure errors.

Thanks again, talk to you on the next thread!!
Giovanni

Hi ,
the errror is the part that we added not in Sterman's model of course....

Thanks!!
G

Hi all, I'm really glad to see that my initial question generated such an interesting thread. Maybe the time are now mature to introduce a bit of "quantitative" or statistical/or "analytical (as we are hearing as the new trendy expression) techniques to manager. I'll try to do it in t...

Hi all, I'm currently working to an extension of one of Prof. Sterman's models with a student. We got an error on the "Fixed Asset" variable due probably to a symultaneous equation condition. The model is attached. Can you help us giving some hints on how to solve it? Thanks in advance!!! ...

Hi Barry,
not sure your last answer is related to my comments, anyway we shouldn't necessarily agree on everything , right?
anyeay, the discussion was interesting for me
Cheers

G

Hi Tom,
I have an old DSS version, not sure which release.

I saved the files as .mdl in the extension and as text files and I opened them with Vensim.

I'll try with the vpm , is the process I followed correct ?

Thanks
G

Hi,
I've tried to get the model from the web, I save them ad .MDL but I cannot open them in a sketch mod just the text file with the equations. If I tried to open the models as sketch I get the message " syntax error". Is this an intended behaviour?

Thanks!!
G

Hi Tom, I'd be interested in having all your different versions of DICE model in mdl format. Would it be possible. I remeber you told meonce that you have a version also set for the optimization. Is it one of the 3 you mentioned? I have another question for you. do you have a detailed explanation of...

Maybe the key point is to convince them that they can count on a group of modelers that can help in solving real issues. The General Motors case studies are an example of that, in the 70' they realized they need a team of "modelers" to help them solving real problems (See Sterman Bisiness ...

Hi JJ, I agree with you that the timing requested by manager is often not exactly the same timing requested by SD. And I agree that managers have "simple minds" as well. An I used to manage people in the past so I know "real life". What I was thinking is to use SD for figuring ou...

Hi Tom, Bob, JJ (et others) I'd like to exchange ideas with you on the following topic. Let's imagine you need to introduce SD to a group of managers that did not have any previous exposure to the subject. You have two hours. Where do you start from? A theoretical lesson with some case studies? Or a...

Thanks JJ, your comments are always valuable.

G

Hi all, I probably asked a too-wide question. The question can be re-forlulated in these terms, according to your experience as modelers what are the statistical techniques that you applied more frequently ? Regressions, time-series modelling (even though I don't think this one will be very useful)....

Hi all,
is there any good book you can recommend about statistical techniques that can be used in SD (for parameter estimations mostly) ?

Or, put another way, what are the techniques that you used most as modellers?

thanks in advance!!
Giovanni

Hi folks I have to export the output of a model into a txt file or an EXCEL file. I need every variable of the model and I'm not interested in getting all the individual time steps, but only the "main ones" (i.e. if the model has a year granularity from 1995 to 2025 I'm interested only in ...

Hi JJ,
as useful your contribution is very valuable!!

Thanks a lot, you gave some interesting ideas to think about.

Cheers
G

Hi there, I'm seeking for material to explain the mathematical theory behind SD. Basically I need stuff to explain what the software (namely VENSIM) is doing "behind the scene". The audience will be a class of undergraduate students in economics. So their mathematical background is not so ...

Hi all,
I'm seeking for the classical article of Hosler, Sabloff and Runge (1977) : Simulation Model Development: a case study of the Classic Maya collapse.

I think it's contained in a book, but maybe someone has a copy of it.

Thanks a lot in advance
G

Hi JJ, thanks for sharing your opinion. I agree with you that from reading and undestanding a model done by others and building a model on your own it's a completely different matter. And I feel myself frustrated when I try to build something new. Apart from academics, did you see examples of SD in ...