Ventana software support forum

Just for completeness with this post: I have just now found some time to work with the aging chain model and I have started to implement Tom's formula to get the leaking work right in the way the model should work out. There are some numerical intricacies here though as can be seen running Tom's mod...

Thanks for helping. While it the Scientific Format suffices as a workaround it does not work properly either - at least if the Reference Manual for Table Tool is to be believed: Scientific puts all numbers in the form 1.0E13, which generally shows more significant digits. I am not seeing any number ...

There seems to be a bug hinting at some deeper issue with some of the analysis tools in Vensim 6.1 (DSS). Take a look at the Graph of this model variable: https://dl.dropboxusercontent.com/u/27062978/VariableGraph.JPG Note that the value within the Time span between 0.5 and 3.0 is around 10.0 . But ...

We do log all bugs in our bug tracking system (even those that we know are user error rather than program error). We work through them on a priority basis, the more people who report them, the higher the priority is to fix it. JJ's report is with the new equation editor, you reported it in version ...

Well, just for the record: I had reported that exact error by mail as early as March 3rd, 2011 ! And here - 21 months later - it is noted as "just raised" in the Bug Tracking System...

I do indeed wonder: Do we have to post all errors on the board to get noticed?

Regards,

Guido

Hi JJ, I can confirm your observation, constants are not highlighted any more. You can nevertheless still change them in the drop-down menu on the main toolbar ("C=1"), once SET is clicked. Unfortunately I am also missing a fix to data variables being - misguidingly - shown without their H...

Thanks for the offer, Tom. I will come back to you should that be needed. Since I will not turn to a C-programmer in this life ( with high probability ;-) ) but have reached a quite sufficient skill level with Mathematica I have developed a solution that should fit my needs. I have chosen to stick w...

Tom, I recently stumbled over the undocumented MARKET MATCH X01 function, also. I am having exactly the many to many problem with different preferences in a spatial problem related to transport modeling (the preference in a zone i for the attractions in zone j is at least distance - dependent). Woul...

Once you are down to Eigenvectors and Eigenvalues for a system of ODEs I would reccomend taking a close look at Mathematica (Wolfram Research). It offers the additional value of being a full fledged CAS so instead of having to go with numbers it will also handle systems symbolically (e.g. you can ni...

Thanks a lot, Tom! That solution works out fine and it does look a lot more elegant than my crude regression attempt. While I have not figured the logic behind your solution completely it looks very much like using the equivalent rate given (conveyance time / time step) - periods of compounding? It ...

Since this thread has been viewed very often I will relay the information given to me by Tony Kennedy (Vensim Support) as I consider it relevant to others: I've raised this as a bug that needs fixing. There is little I can do for now about it, but it is in our system now so hopefully will get looked...

I had posted the wrong link to stackoverflow - a help site - here is the correct one:

http://stackoverflow.com/questions/4219 ... ice-64-bit

I had a similar problem trying to run a Vensim 32 Bit DLL from Mathematica (64 bit). There it was possible to force Mathematica to run its 32 Bit kernel which then works. There seems to be a workaround for Office 64 Bit as far as stackoverflow (older version of stackexchange) suggests: http://blog.m...

Hi, this almost seems to trivial to ask - especially for a long time user - but I just now noted a strange issue with locking windows: In a model I was using the table tool to check some variable's behavior. I used the lock-option to keep variables shown and to be able to compare them. To resize the...

Thank you, Tom. The leakrate as it is implemented in Vensim's Conveyor Delay in its present form is misleading. In a conveyor the inflow is pushed through the conveyor stock as it is so the profile of the inflow in time remains the same. If the fraction leaking is 100% (independent from the rate of ...

While I am waiting for further answers regarding my problem with a conveyor based aging chain I have been trying to get some more hold upon the problem at hand. I have enclosed a simple model of a one stage conveyor delay that pretty much uses the standard formulations as provided in chapter 9 of th...

Tom & Tony, thanks for putting me on the right track - I have simply not been able to spot the error in the equation after looking and looking. But there remains a problem that I am not able to solve: I have enclosed the (corrected) and modified aging chain model using conveyors. In the model I ...

Duh!!!

Thank you, Tony.

- That leaves the problem of getting the 1 to walk across, instead of two fractions....

I have enclosed the model here.

Guido

Hi, I am experimenting with different formulations for an aging chain for vehicles (or other assets for that) where it is somewhat important to correctly report the age distribution. Since the usual coflow formulation will assume average attributes to be passed along it is imo not appropriate when a...

Hi, I just found this post while searching for Powell optimization and I have a similar question as JJ originally posted: Does Vensim make use of Brent's modification of Powell's optimization method which is so favoribly hinted at in the Numerical recipies? I recently found that the Brent-Powell or ...

Great! ... and the cumulated effect of all those 'minor' improvements will be a greatly reduced switching probability for all Vensim users

Keep it up, Guido.

Tom, thank. Ok, the bottom menu is a partial solution since I can put an auxiliary on the sketch, select 'box' down there and still find it to be an auxiliary/constant in the equation editor. What I wanted is that my choice of default shape for the sketch tool "auxiliary/constant" will not...

Still beats me since the "box" does not fall from empty space on a sketch and then has to be interpreted but is put there by the modeler who has used the sketch tool for auxiliaries/constants to do that (on purpose!). Since Vensim does "know" which tool is used when a variable is...

In Vensim if a variable is drawn with a box Vensim will automatically assume that it is a level. Why so? There are two sketch tools, one for auxiliaries/constants and one for boxed vars/levels. Why not use that information and "trust" the modeler that he knew why he wanted an auxiliary/con...