Ventana software support forum

Hi Tom, thank you for your reply. I am aware of what the Kalman-Bucy Filter (FIMLOF) will do; what it does is - in my opionion - nicely described by Peterson in his article as provided by Randers (while it is older I believe). It is a tool very appropriate for a system where driving and measuring no...

Hi Tom, I do not see any reason for using a DELAY FIXED here. You can handle discrete systems - e.g. difference equations' systems - using the regular System Dynamics notation. What you need to do is: 1. Set the time step to 1. 2. Convert the Stock Equations into difference equations, e.g. Delta X =...

Dear All: I still have some questions left regarding how calibration is handled by Vensim Pro/DSS. But let's just wrap things up as far as have understood calibration in System Dynamics in general. I have enclosed three charts from the excellent paper by Peterson that is part of Jorgen Randers' &quo...

Hi Paul, I do not know about Visual Studio but you should get all you want by running your model saving the runs to 'runname.vdf'. You can then go to the menu and choose 'Model>Export Dataset...' from the main menu. This let's you choose your saved runs and convert them into excel of tab delimitered...

A couple of open questions (cf. the thread so far) have remained unanswered and I would appreciate some remarks. I have tried to answer the second one by experimentation. So it seems that if I have an exogenous data file which only has data for one point in time (eg. from converting a .dat file or a...

Hi Johann, take a look at the user's guide that comes with Vensim and look up how Vensim uses external data files in the vdf-format for data variables and how reference modes are used (like a run that is saved and then loaded for comparison). If somewhere in the settings for the model you have told ...

After having started a fruitful discussion about 'dealing with bigger models' I was recently guided to Nathaniel Osgood's papers dealing with the comparison between ABM and SD. In this paper he dares to give some outlook for the future of both modeling worlds and notes, that both worlds will probabl...

JJ, yes, I can see what you are saying. You are using the RC statements (behavior-behavior) statements quite the same way a reference mode ist used: It defines the model boundary and at the same time the model verification. Actually it is collecting 'all' possible modes of behavior that you can thin...

Hi JJ, it is too bad that I will not be able to attend the conference this year but I certainly hope to meet you and other modelers in 2012. Your approach to modelling by using RC statements to ensure a very concise top-down approach is very attractive and certainly true to modeling for understandin...

Hi JJ, that may be your experience and it does sound plausible but it is nevertheless not a logical necessity (for the rhethorically inclined readers: your statement is a bit like pascal's wager 8) ): e.g. you may do good thinking and use more computer power at the same time. Another way to put it :...

Tom, thank you for making this clear. The fog has cleared a great deal by now and just a couple of questions remain: In the simulation control there is a tab called 'advanced' where there is button fro 'Minimal Memory'. How will that really help? In reading in external data with more than 2 subscrip...

Thank you both for valueable advice, I just went ahead and experimented with a model containing only a subscripted variable big var with two subscript ranges (750x750). If I set this matrix to be filled with '1' - big var being a constant the vdf for the run will have the size of about 5 MB. If I we...

Dear all: So far - not having a computer science background - I had the more or less naive impression that computers by now would have surpassed any limitations previously imposed on building models (that I could thing of at least) regarding performance and memory. So I had thought. Having recently ...

Thank you, for providing a workable solution - for now I had to reinstall a second display ...

If there is a software feature that will make such procedure a bit more user friendly please add it to the wishlist of (minor) improvements to VENSIM...

Kind regards,

Guido

Sometimes the simple tasks are difficult: I was using an external monitor showing a model recently and had moved my Vensim model to the second screen. When I later had disconnected the external monitor and restarted Vensim, the equation editor window would not show. Unfortunately all other window op...

Many of the improvements that have been mentioned here are right on the spot and would make life with Vensim more enjoyable: e.g. directly reading numerical values from graphs, improvements with reality checks (JJ: they are indeed very worthy to keep) and so on. I would like to propose a much more m...

Hi Nadine, I would take a closer look at Jack Vennix (1996): Group Model Building - Facilitating Team Learning Using System Dynamcis, Wiley & Sons (ISBN: 978-0471953555). There are some good hints at how to use facilitation and interviews to elicit SD-models. Also take a closer look at Dr. Venni...

JJ, thank you indeed for being engaged in this discussion it certainly is quite rewarding - especially since it got me to take out my notes from Bob's course again and to remember the nice features of Reality Checks. As to your understanding my posts: It was actually a quite "trivial" but ...

The Formula for the average content in the stock has been corrected to:

AvgInStock = [Stock(t) + Stock (t-1)]/2

Sorry for (previous) "sloppiness"...

Guido

Hi JJ, thanks for pointing at chapter 14 in the User's Guide to Vensim and to hinting at how to turn passive RC to active RC and on to how to have RC work as a check to the fit of the model to data. I wondered about checking the fit when reading the most interesting article by A. Graham about "...

JJ, thanks for the interesting posts albeit the first one comes to me like a chinese fortune cookie: It all depends on the purpose at hand and there is no theory of model building ;-) So far my personal road of learning has been: 1. Kim Warren does have a point in the way he presents a strategic arc...

Thank you. I have mailed the settings to Vensim@Vensim.com since for reasons of disclosure I would not like to publish it here.

Kind regards,

Guido

Hi, I noted that there is silence on this post which maybe is due to my touching an old issue with a beard as long as...? Nevertheless as to Kim's opinion on the difference between an annual model with DT=0.25 and a quarterly model with DT=1 I have just now come upon Andrew Ford's remarks in "M...

Hi, for some reason I do encounter problems when publishing packaged models for use with the model reader. Even with very simple models that do not contain anything else than the model and a base run people I have emailed the package complain that they get a message warning that some logical path co...

Tony, I have exchanged the .vpm-file - but I wonder why it failed?! (maybe a path-problem) - and I have enclose the model. In my opinion Kim does have a point as flow-integration will give bad results for DT=1 and the averages are more intuitive. I also have to add that the point with the meaning of...