Ventana software support forum

Is it possible to define a lookup table so that it chooses the output as a variable in the model rather than a number; so for example:

The lookup data set would be some thing like [(1, VarA), (2,VarB), (3, VarC)]

Thanks Admin (Tony, Tom?! I'm going to try it out and might have to get back to you! JJ, good to hear from you! I have built a high level model which works very well - sometimes, no matter how silly it may seem, it is also important for a good modeller to do what the client wants to make sure his/he...

Hi Folks! It's been a while! I have an interesting problem to deal with. I'm running a model in hours for a year - this is a client specification. I need to create an electricity load profile for a campus, for which I have data for different buildings over a twenty-four hour period over 3 seasons (s...

Thanks Tom! I presume I could try an ODBC connection from Vensim to Excel, on the lines of the Mohammed Jalili's tutorial too?

Hi everyone! I hope everything is going well with the Ventana community. I should have asked this a long time ago: St**la has a feature which creates a "persistent" link to an excel file and allows you to drive the excel file from the SD model - no programming required and very useful when...

You can open multiple instances of an app in OSx via the Terminal window: Go to Applications->Utilities-Terminal: type in the following command "open -n "path/to/file.extension" You can also create a macro for Vensim using Automator: http://lifehacker.com/5668648/automate-just-about-a...

What a wonderful tutorial!

Hi Rolf, this is very interesting; I'm curious, what happens to the results of the outflow with regard to your expectations, if you put the Delay Time value = the mean delay of your pdf?

Hi! a Units Check (Ctrl U) shows that many formulations don't make sense; I'm not sure what these assumptions are based on, so I can't say that they are wrong; however, for example: Your variable "Birth rate A" should have units "1/Month", so that when it multiplies with the Popu...

Thank you both very much!

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...

Greetings,

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

Karan

Hi adjie,

Tom's right and if I have read and understood your post correctly - when you have a model with non-linearities, you can't pre-determine, or categorize which variables based on their sensitivity to inputs.

My Best,

Karan

This is sweet. Thank you so much!

Would it be possible to pass on content as well as post data/metadata?

Karan

Hi Tony, you mentioned the possibility of activating an RSS feed for the forum a while back - is this still a possibility? It would be very useful!

My Best,

Karan

Hi Milad, if you do a search for optimization in this forum, you will find plenty of useful information on both the algorithm as well as on how and where to use it effectively.

My Best,

Karan

Hi JJ, Thanks, but this is still one step removed; would like ghost variables (except stocks) to accept inputs without additional steps.

It would be nice if Ghost Variables could accept inputs as well, this is particularly useful when you are working across multiple views!

Hi Ashish, Principles of Systems by Jay W. Forrester, Business Dynamics by John Sterman, A Practical Approach to SD Modeling by Goeff Coyle are great places to start. As for having a variable increase or decrease 10% year by year, it is best to treat it is a stock with an initial value and let it gr...

I agree with Tom, building a Stella model from scratch in Vensim is a great way to learn about the software and the system you're studying in general. I have seen a lot of Stella models recently, which have been built without any attention to units or basic modeling fundamentals. Though I enjoy usin...

Greetings!

I would also like to see a Stock "non-negative" feature, specifically for Vensim PLE; often, in my short introductory workshops and courses, students at this early stage of learning get lost with MIN, MAX, non-linear formulations for flow control.

My Best,

Karan

When viewing a graph, it would be helpful to be able to tell the exact value of the variable of concern as one scrolls along the independent axis. This would save an intermediary step of having to open up a table.

Hans, if you haven't already, you may also want to take a look at Business Dynamics Chapters 17 and 18 which deal with instability and oscillations using the example of a manufacturing supply chain.

Hi Han, could you please post your vensim model file?

Hi amatriciana85, Please attach your file, I can take a look.

Karan