Ventana software support forum

Old hat, but for univariate sensitivity analysis would like to be able to assign specific values to a parameter; then simulate the corresponding behaviors of a pre-selected variable within one operation. If Vensim already does this please let me know.
Thanks,
Steve Arquitt

There are some great suggestions here, and they're on our development path. Keep 'em coming!

Tom

Request #1:

Refer to User’s Guide
Section 15 Sensitivity Testing
Confidence Bounds ; cash flow:Sensitivity Graph

It would be nice if one could add an exogenous data time series to this graph.
Such that you have the mean value and confidence bounds from the sensitivity run as shown in the User’s Guide
PLUS another exogenous cash flow variable plot that had nothing to do with the sensitivity simulation run results.
That is picture the cash flow:Sensitivity Graph shown in the User’s Guide Section 15
with another separate squiggly line spanning the 0-60 month time frame.


Request #2 : Enhancement to the Loops Tool

For larger models it would be nice to be able enter a set of variables
and have Vensim return all the loops that include the entered set of variables.
So lets say a model has 26 variables a-z .. what would be nice would be the ability
to enter ‘h’ , ‘n’, ‘t’ & ‘y’ in the Loops Tool
and have loops tool return all the loops containing these four variables.
That is each loop shown would include all four variables.

Hi,

since I used to work with i-Think a bit I noted that the concept of modules there is a neat one. I am not a computer expert but I would assume that this comes a bit closer to object oriented approaches to code/models. To me the reuse of Vensim models (especially if large and subscripted) tends to be a bit cumbersome. (If there is good advice how best to do this, in text editor or sketch mode I would be more than glad to know.)
It seems to me that to make a view (or maybe a group) be some encapsuled structure may be a nice feature. So in order to reuse parts of models it would be great if the sketch information would be made locally available instead of being dumped at the end of the whole model. Then a certain substructure of the model could be more easily copyied with all information pertaining to it. Maybe such structures can be saved on their own? (I do not know if this is possible with the molecule-feature of Vensim?)

In i-Think the linkage of modules/submodels is automatically plotted in an aggregate view that shows the model structure from a high level perspective (a bit like the subsytem diagrams). This - or something in the line - would be a neat option to have in Vensim where you have to build this kind of navigation by hand using links and commentaries.

Kind regards,

Guido

Hi

One feature that should be added, is to make Vensim work in static mode, with no levels and no time periods. Presently if one wants to work in static mode, it is better to work with two periods, a 0 and 1 for instance that will show two identical values for the two time periods.

The version working only in static mode could be much cheaper with eventually different versions too. It would have the great advantage of permitting people to be trained relatively quickly to perform useful simple static works by themselves as they do with spreadsheets.

Presently people who want to use a tool like Vensim, after a two months intensive training will not be able to work with it usefully to my opinion because they are not used to think dynamically and that most of their problems are considered statically unless they have already gained a lot of experience making static models using tools like those used in Vensim.

If they work first statically they may use tools like reality checks, sensibility analysis, synthesim, optimization (not games) etc… and get progressively acquainted with them. After quite a long time having learn to build useful static models, eventually after several years, they may be tempted to step to a dynamic universe, which will be much easier to grasp, having already used the tool in a static way. This way it would be possible to make SD a more popular tool instead of a secret, sophisticated tool reserved to an elite.

Of course it would be necessary to write a static user guide with static examples and to make some modifications to Vensim when used in a pure static way to boost its ease of use.

The Analytica software is doing that and I think that most of their clients use the tool only in a static way and the Dynaplan software is too supposed to be working too in a static or dynamic way.

Regards.
JJ

Hi,

even though it may be a bit heretical I would like to draw your attention to a leading competitor (Powersim) that has recently released the Studio 9:

http://www.powersim.com/main/products__ ... s/premium/

http://www.powersim.com/main/products__ ... lingtools/

So there is 64 Bit, dynamic subscript ranges and a very modern look and feel - I know at a quite higher price. But that seems to be something you will have to figure out. The look and feel of Powersim (if you are not just aming at the academic market only) and the trusted and fast running engine and features of Vensim would make a great combination.

Regarding external functions: While Visual Basic is a slow approach it probably allows to do external functions rather easily. Maybe there is a way to allow for a rather "embedded" way to do this?
Please be bold in your redesign of Vensim!

Kind regards,

Guido

I would like to see a more (particularly for beginners) user friendly reference mannual and help system. Some SD models can be used as tutorial vehicle and enormous aspects of devepment and simulation of SD models can be discussed in the manual's chapters step by step adding more information in each chapter of the manual. This would allow to give the modelers advices to fix problems and errors that they might face in each stage. For example I had developed a macroeconomic SD model using Dynamo language and had applied optimal control theory to analyse the trade off between economic policies and targets. In the model there are (four) table functions (lookups in Vensim) to calculate trajectories of the so called Ricattii equation. These lookups (CKij in the model) consist an auxiliary equation (Cdelta). Using a software of Dynamo I did not have any problem simulating this model. But when I rewrite this model in Vensim the model would not simulate. While equations are ok in equation editor but an error messages appear indicating that "the CKij are special types and cannot be used as normal variables". Yet in the reference manual one cannot find why these equations are special and cannot be used as normal variables and what should be done to solve the problem. When I tried to get help from the help forum I am advised to try to pass some arguments to lookups. Yet there is no instruction how this should be done. I hope the errors that users of the software encounter and report are given more careful consideration and they way these errors should be addressed are discussed in the online help system and in the future reference manuals.

Mehdi

More memory (eg a 64 bit version).

More informative error messages.

A less techy look to it (I can't be very precise here, but ithink and Powersim both win on looks, if not technical capability)

Tidy up the menu structures (eg why are 'model settings' and 'simulation control' in different places?)

Clearer documentation (even tho' I've been using Vensim for years, some of the documentation is a complete mystery to me)

An easier way into Venapps, preferably a completely new product - maybe use Sable?

It would be very useful to have a tool to select all polarity marks of arrows to highlight them in the diagram.
Best regards.

Some of these things will take a while, but we're listening.

There should have a suggestive window after simulation run relating to wrong usage of unit name. If there will be some suggestive comment relating to model, it would be helpful for the modeller to fix their model

I would have the following additions (I have not checked for duplicity so someone may have suggested this also):

• I would like to have the graph toll and the strip graph tool show a data variable that has been read in as :HOLD BACKWARD: or :LOOK FORWARD: in its correct form, e.g. as a step-variable instead of the rather misleading representation as an interpolated variable that is the present state of affairs.
• It would be nice to have an office-like paste brush to rather quickly format sketch elements.
• As has been already suggested I miss a way to select say multiple stock and then format all of them at once (maybe I simply do not know how to do it?).

Kind regards,

Guido

Hi!

Great and powerful product folks!

Some potential improvements I have thought would be good and would make my life a little easier, (some of which have been mentioned above but I would like to reiterate):

- When data is brought into Vensim using :Hold Backward: etc then charts of this variable display the appropriate shape
- A wizard to help guide the user though setting up Vensim to run compiled models
- A way to export the data used to generate a sensitivity chart (i.e. the percentiles over time)
- get data from excel in more than 2 dimensions
- when defining the sensitivity analysis distributions have some way of displaying the defined distribution as a graph (e.g. triangular distribution, etc) to provide visual feedback
- Some way to change the background colour for boxes and other shapes using a button in the main interface (as per font colour, font size etc)
- The ability to fill in pipes with a selected colour
- More configurable custom graph, e.g. font size, bar charts etc
- more resizable control (e.g. custom graphs, sensitivity control) so that it is possible to see the full strings, e.g. for long variable names
- button on the Sensitivity Simulation Control (and other places) to create new Sensitivity Control file, savelists etc
- A better and more straightforward way to develop great looking user interfaces

Cheers.

Hi,

At my company we continously re-use a standard model, and we would like to reduce the effort required to do this, to set up a new instance of the model. For that, being able to add new elements to a family of subscripts at the touch of a button would be great - especially if that could also be done via scripts (VB, C++,...)

Of course, in order for that to work effectively Vensim would also need to pre-populate these new elements with appropriate values for tables and parameters - ideally, by using the values of a specific existing element specified by the user.

Any chance of any of this happening any time soon?

Thanks for all the great work!

Alex

At my company we continously re-use a standard model, and we would like to reduce the effort required to do this, to set up a new instance of the model. For that, being able to add new elements to a family of subscripts at the touch of a button would be great - especially if that could also be done via scripts (VB, C++,...)

Have you tried the "GET ... SUBSCRIPT" functions?
http://www.vensim.com/documentation/ind ... script.htm

Hi everyone,

I'm a Vensim beginner. Not sure if anyone suggested before a "hand tool" that can pan the model view like that in a pdf viewer?
It would be useful to have when connecting variables far apart in the screen. Thanks.

Tailin

If you right click with the mouse when you have the hand tool selected, you can pan around the view.

Thanks! I will put more efforts on checking out the manual. ^^

One thing that I really feel the lack of it in Vensim is the fact that it is not possible to assign different time steps for state variables. I mean for example if you have two state variables, for one of them you want to do the modeling in monthly time step and for the other one you want to use daily time step. I know there are tricks to make it possible but I was wondering if you can assign put a module in the vensim that the user can define the time step to be used for each state variable.

Differential time steps would be much harder to implement than it sounds ... why do you need it?

Yes. That's true especially when you want to develop a general framework suitable for all users.

I don't need it now. But when I was doing one of my projects, I needed to develop two different types of models and integrated them in a single Vensim model. The output of the first model generates the input for the second model. The first model should be run in daily time step but the second model in monthly. So in that time I was thinking of developing two different models and integrate them by DLL feature. It worked but it was not as user-friendly as it could be in a sole Vensim model.

Anyway, when I noticed this post, I was thinking maybe I can put my own challenge for you so that you might have an idea how to implement it in Vensim.

Majid,

Thanks for asking the suggestions.

I may like to suggest the following:

1. VENSIM Software should provide easy facility to attach Table function between two variables (It is required, in case the variables are linked through tabular data, when there is no equation between the two variables).

2. PLE version of VENSIM Software should provide facility to open 2 or more windows at a time (for viewing two applications at a time, without closing the previous model, if we want to view the next model).

Thanks

Table functions (called Lookups in Vensim) are available: http://www.vensim.com/documentation/usr08.htm

You should be able to launch 2 copies of the program. Higher versions of Vensim permit opening multiple models within a single application.

Well, I would like Vensim developers improve the application's GUI (Graphic user interface) I think it's a little old!

It would be really nice to have a ready-made function for a second-order system (similar to DELAY1 or DELAY1I for a first-order system), i.e. a system behaving according to the following differential equation:

T^2*d^2y/dt^2 + 2*D*T*dy/dt + y = u

y(t) and u(t) are the output and input of the system, respectively. T is the time constant and D the damping ratio of the system.