[BEGINNER] A few questions

[tailinhuang]

Hi,

I just started building my very first model with Vensim. I have a few rather basic questions for you:
1. I have now a model of over one hundred variables in 6 different views and would like to know exactly how many variables in total as well as in each views. Is there a simple way to get the statistics?
2. Is there a way that I can output a table showing each variable with the numbers of other variables that affect and being affected by the variable (instead of counting them one by one)?
3. Also a similar table, but showing the number loops that each variable involves?

Thanks a lot!

Tailin

[Administrator]

Can you enter your serial number on your profile please, you selected that you use DSS, but entered 0 as the serial number.

1. I have now a model of over one hundred variables in 6 different views and would like to know exactly how many variables in total as well as in each views. Is there a simple way to get the statistics?

Click Model->Settings, and then select "Info/Pswd". There is a "model info" section here which will tell you these things.

2. Is there a way that I can output a table showing each variable with the numbers of other variables that affect and being affected by the variable (instead of counting them one by one)?

Causes and uses tables. Right click on the table tool, and select causes/uses from the "show link or sketch vars" dropdown box.

3. Also a similar table, but showing the number loops that each variable involves?

There is a loops tool as well.

[tailinhuang]

Thanks for the prompt response. I have attached the serial number in my profile.
The table tools requires the model being able to simulate, but we are currently in the stage of building a qualitative causal-loop-diagram. Is there anyway around in this situation?
It seems that counting loops with the loops tool needs to be done one variable at a time. But for hundreds of variables what can we do?

The problem we encountered may be a general modeling question. We kept building our causal loop diagram for a while (now 203 variables), but now feeling a bit overwhelmed and trying to simplify it.
We are thinking if we have a table listing the numbers of causes, uses and loops of each variable, we may be able to decide which variables are more important.
Any suggestion for this kind of situation? Thanks a lot.

Tailin

[tomfid]

There's also a nice documentation tool, from ANL - see http://models.metasd.com/vensim-model-d ... tion-tool/ for a link. I'm not sure how well it will work on a CLD that doesn't have equations though.

You could probably use the .dll to automate a loop count. However, I'm not sure it'll really help that much. The number of loops a variable is involved in is a weak indicator of its importance, because it's the gain (strength) of the loops that matters. It's probably fair to assume that a variable that's in a lot of loops is important in some sense, because if it weren't, you wouldn't have thought of all those links. But it could still be the case that the variable is not a useful policy lever (e.g., because all the loops are negative, and balance the effect of a change in the variable). Also, the inverse is not necessarily true: a variable in few loops could still be important.

[tailinhuang]

Thanks a lot. I'll research a bit before asking further questions.

Tailin

[tailinhuang]

Dear experts,

I have a follow-up question regarding causal loops. Suppose that I identify 3 (or more) seemingly important variables in my model (which has now 207 variables), is there a way to know what are the causal loops that includes all those 3 variables? We would like to analyze the model structure (qualitatively) and see if there is any interesting loops to investigate further. Thanks!

Tailin

[Administrator]

All I can suggest is using the loops tool and then copying the output to Excel and try and match those which include the parameters you are interested in.