Ventana software support forum

I think there is too much hidden in the 'Control Panel'. In particular, both datasets and graphs could be separate icons. When I first use vensim after not using it for a while, it always takes me some time to remember where to find these functions.

Thanks to you both Bob - I will amend as you suggest and have another look. I think you are correct that the problem is initialisation. I hadn't thought it through, but I think I had assumed that the items already in the stock had all entered in the previous timestep (clearly wrong) so the shape dis...

hi JJ

I'm not really sure what you're suggesting here. I agree that you need to understand a function before using it and that a simplistic (toy) model is the best way to understand. That is exactly why I built the file I attached. It is a simple model to help me to understand how profiles work.

Jen

Hi JJ I just constructed the example to demonstrate the problem, it's not a real problem at the moment. I originally thought I would have to use a QUEUE FIFO in my current model and couldn't get initialisation of the queue to work, which also uses shape/profile concepts. To try and fix it, I dug out...

I am having difficulty working out how to do shape profiles. I think I have asked a similar question before and thought I knew how to construct these correctly, but I am getting odd results. What I would like to do is have a shape graph and a mean variable. For each timestep, the variable's value is...

Thanks Bob. If I use ACTDrugs.mdl, I get a different error about needing a published model. What's the vmf file?

Okay, for some reason this method is no longer working for me and I can't quite figure out why. I build the model as a mdl file (with Interface.xls as the interface). I have published a vpm model to be called by the Excel file and am trying to publish the vpa version for user testing. I open the mdl...

Thank you both. It is now much more sensible. cheers, Jen

As part of a drug treatment model, I am trying to prison sentences. That is, there is a stock of current prisoners and a delay function is needed to control their outflow. Prison sentence durations are right skewed (large number of short sentences, small number of much longer sentences). In practice...

Originally posted by bob@vensim.com
As long as you are not truncating the table - and not really any reason to do this you could simply use

TargetMin + (TargetMax-TargetMin) * RANDOM LOOKUP(DelayShape, 0, 1, 0, 1, 0)

that should fix the units problem.

Thanks, much more elegant

Sorry, one more minor problem. I am still having unit incompatibility issues. The stretch parameter is expected to be dimensionless. This works fine in the conceptual world because: stretch = (outMax-outMin)/(inMax-inMin) where in and out denote the input and output distributions. In this situation,...

Thanks Bob. My random lookup is now doing what I expect. Of course, I still have to make the delay work properly:)

Jen

Thanks Bob. The way I would expect it to work is something like: 1/ Convert 'probability function' to cumulative function 2/ Normalise to cumulative probability function by dividing cumulative function by total 3/ Then I think you need the inverse of that function, so that 4/ From a uniform random d...

Thank you for the response. I have revised the model to reflect the min/max use of rescaling. However, I interpreted the lookup input as the probability density function (without worrying about integral being 1). I have used a strongly skewed input test function and the output of the random lookup i...

Model attached

Originally posted by bob@vensim.com The first argument is the name of the lookup function that describes the shape of the distribution. EG uniform lookup((0,1),(1,1)) Note that the x range does not actually matter as Vensim integrates the lookup and adjusts everything to give the mean value specifi...

I have decided to post the files here rather than have people contact me as I have not been developing the interface further and several people have been sent the files already. I would appreciate any improvements, questions or comments to be posted here. The interface has internal comments in cells...

Okay, I have an Excel interface with a Vensim model. I built the interface in Excel 2007 but saved it as Excel 2003 (ie xls format). I published the model but the user received an "Extraction error" when opening. The interface is working fine despite this error. I am not getting an extract...

Excellent. I believe I have it now. The following is partly for confirmation and partly for anybody else reading this with the same problem. During development: 1/ Build Vensim model 2/ Publish Vensim model as Package Type "Model" so as to make vpm file that can be called by Excel 3/ Build...

Thank you both for your help. It is difficult to test these things without access to a spare computer without DSS installed. I have a follow up question about packages (probably for Bob). The manual states: One consequence of this structure is that all models and supporting files must be in a single...

hi all I have noticed a few people asking for code to connect Excel to Vensim. I have developed a general purpose Excel interface that delivers basic Vensim functionality (running scenarios and sensitivity analysis) and can be used on any model by changing variable lists on an Excel sheet. Please em...

I have prepared a model (using DSS single precision version 5.7) for an educational institution that has version 5.6B of PLE installed. I have published my model as a vpm, with all versions of Vensim checked. The model has an Excel 2003 interface and works on my machine. On their machine, the Excel ...