Search found 22 matches
- Sat Jan 15, 2011 8:33 am
- Forum: Vensim
- Topic: What improvements would you like to see in Vensim?
- Replies: 150
- Views: 16777215
Re: What improvements would you like to see in Vensim?
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.
- Tue Oct 06, 2009 10:57 am
- Forum: Vensim
- Topic: Profile shapes
- Replies: 7
- Views: 7086
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...
- Tue Oct 06, 2009 9:05 am
- Forum: Vensim
- Topic: Profile shapes
- Replies: 7
- Views: 7086
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
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
- Mon Oct 05, 2009 10:16 pm
- Forum: Vensim
- Topic: Profile shapes
- Replies: 7
- Views: 7086
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...
- Mon Oct 05, 2009 11:21 am
- Forum: Vensim
- Topic: Profile shapes
- Replies: 7
- Views: 7086
Profile shapes
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...
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...
- Tue Nov 18, 2008 8:56 pm
- Forum: Vensim
- Topic: Initialising delays
- Replies: 3
- Views: 4297
- Sat Nov 15, 2008 12:01 am
- Forum: Vensim
- Topic: Initialising delays
- Replies: 3
- Views: 4297
Initialising delays
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...
- Wed Nov 12, 2008 5:05 am
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
Thanks, much more elegantOriginally 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.
- Tue Nov 11, 2008 11:49 am
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
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,...
- Mon Nov 10, 2008 1:16 pm
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
- Mon Nov 10, 2008 11:43 am
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
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...
- Sun Nov 09, 2008 1:57 pm
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
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...
- Sat Nov 08, 2008 10:13 pm
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
- Sat Nov 08, 2008 1:51 pm
- Forum: Vensim
- Topic: How to use "Random Lookup"
- Replies: 28
- Views: 48958
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...
- Thu Sep 18, 2008 2:17 pm
- Forum: Vensim
- Topic: Excel interface for Vensim
- Replies: 1
- Views: 3782
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...
- Fri Jun 27, 2008 2:03 am
- Forum: Vensim
- Topic: Extraction error
- Replies: 1
- Views: 2824
Extraction error
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...
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...
- Wed Jun 25, 2008 7:29 am
- Forum: Vensim
- Topic: Excel interface for Vensim
- Replies: 1
- Views: 3782
Excel interface for Vensim
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...
PLE dll
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 ...