Search found 4011 matches
- Sat Jul 05, 2025 8:38 pm
- Forum: Vensim
- Topic: Modelling small discrete flows
- Replies: 6
- Views: 264
Re: Modelling small discrete flows
This is an example of how I'd tend to do it:
- Fri Jul 04, 2025 12:13 am
- Forum: Vensim
- Topic: 3rd Party Tool SDM-Doc
- Replies: 2
- Views: 122
Re: 3rd Party Tool SDM-Doc
I've messaged them.
- Thu Jul 03, 2025 10:45 pm
- Forum: Vensim
- Topic: Modelling small discrete flows
- Replies: 6
- Views: 264
Re: Modelling small discrete flows
Can't run this without the data spreadsheet.
Could use units.
Could use units.
- Thu Jul 03, 2025 10:43 pm
- Forum: Vensim
- Topic: Modelling small discrete flows
- Replies: 6
- Views: 264
Re: Modelling small discrete flows
The downside is that Poisson/binomial processes make the model stochastic, so you need to do regular sensitivity runs to appreciate the diversity in behavior.
- Thu Jul 03, 2025 10:40 pm
- Forum: Vensim
- Topic: Modelling small discrete flows
- Replies: 6
- Views: 264
Re: Modelling small discrete flows
I think to do this right, you need to randomize the small flows rather than accumulating fractional people until you have a whole one.
Examples:
https://vensim.com/2017/01/discrete-stochastic/
https://metasd.com/2017/10/bernoulli-poisson-bar/
Examples:
https://vensim.com/2017/01/discrete-stochastic/
https://metasd.com/2017/10/bernoulli-poisson-bar/
- Wed Jul 02, 2025 2:56 pm
- Forum: Vensim
- Topic: Dump warning in log file
- Replies: 2
- Views: 156
Re: Dump warning in log file
I think you'll find some error logs in
C:\Users\yourname\AppData\Roaming\Vensim (shorthand %AppData%\Vensim )
C:\Users\yourname\AppData\Roaming\Vensim (shorthand %AppData%\Vensim )
- Mon Jun 30, 2025 5:06 pm
- Forum: Vensim
- Topic: Multiple Equations for a Subscripted Variable HELP
- Replies: 1
- Views: 461
Re: Multiple Equations for a Subscripted Variable HELP
You've found a glitch that will be fixed in the upcoming release. You can't literally write, Price[sector,sector] = blabla but you can define subscript equivalents, fromSector <-> sector toSector <-> sector and then write, Price[ fromSector, toSector ] = blabla However, the equation editor glitch cu...
- Mon Jun 30, 2025 3:49 am
- Forum: Vensim
- Topic: Lookup selection IF THEN ELSE()
- Replies: 1
- Views: 778
Re: Lookup selection IF THEN ELSE()
IF THEN ELSE(fluid=1, fluid1 lookup(input), fluid2 lookup(input))
- Fri Jun 27, 2025 8:46 pm
- Forum: Vensim
- Topic: X IF MISSING / IF THEN ELSE
- Replies: 2
- Views: 2199
Re: X IF MISSING / IF THEN ELSE
X IF MISSING is also more convenient if you have multiple data inputs in the equation.
- Fri Jun 27, 2025 8:45 pm
- Forum: Vensim
- Topic: How do I use the compiled model with command script CMD
- Replies: 3
- Views: 3310
Re: How do I use the compiled model with command script CMD
The other option is to package the model as a vpmx along with the compiled .dll.
- Fri Jun 27, 2025 3:59 pm
- Forum: Vensim
- Topic: Export results from sensitivity analysis in xlsx format
- Replies: 1
- Views: 239
Re: Export results from sensitivity analysis in xlsx format
I don't recall if xlsx is supported, but CSV and tab-delimited are. Model>Export Dataset...
CSV opens into Excel by default.
CSV opens into Excel by default.
- Wed Jun 25, 2025 6:18 pm
- Forum: Vensim
- Topic: Copyright World3 Model
- Replies: 2
- Views: 4880
Re: Copyright World3 Model
I think you are certainly safe to extend and adapt World3 however you wish. Obviously it would be a courtesy to cite the original authors, whether or not it's strictly a legal obligation - which I'm sure you would. The Vensim license only applies to Vensim and ancillary components - anything you cre...
- Fri Jun 20, 2025 8:36 pm
- Forum: Vensim
- Topic: Non-integer Poisson Warning
- Replies: 2
- Views: 659
Re: Non-integer Poisson Warning
It still computes the payoff; fortunately that works because it uses the LogGamma function as a continuous generalization of factorial. Should be harmless, though perhaps we should suppress excessive warnings.
- Tue Jun 17, 2025 4:33 pm
- Forum: Vensim
- Topic: Resize first column of table?
- Replies: 3
- Views: 790
Re: Resize first column of table?
You're right ... as of at least 10.1.5 (Win) it was possible. So, regression ...
- Tue Jun 17, 2025 4:06 pm
- Forum: Vensim
- Topic: Resize first column of table?
- Replies: 3
- Views: 790
Re: Resize first column of table?
I'm not sure it was possible, but obviously it should be. In the old gui, it was possible to right-click (ctl-click) the table tool to change the default width. Also, the runname should be in its own column. Ticketing for improvement ...
- Sun Jun 15, 2025 10:14 pm
- Forum: Vensim
- Topic: What does fp_err_ctx do?
- Replies: 2
- Views: 1019
Re: What does fp_err_ctx do?
These _should_ replicate an fp error. We'll take a look at the model. You might try turning on the payoff report, if it isn't already on, to reproduce.
- Mon Jun 09, 2025 3:17 am
- Forum: Vensim
- Topic: Can I vary the NOISE SEED in the .vsc text instead of the checkbox?
- Replies: 2
- Views: 2013
Re: Can I vary the NOISE SEED in the .vsc text instead of the checkbox?
Not if you're using the File method. But every time you run an mcmc, it now generates a vsc that runs the sample with that box checked.
For other methods (multivariate, latin hypercube) you can add NOISE SEED=VECTOR(...) to the list as an alternative.
For other methods (multivariate, latin hypercube) you can add NOISE SEED=VECTOR(...) to the list as an alternative.
- Fri Jun 06, 2025 2:42 am
- Forum: Vensim
- Topic: Does running Powell using DLL/Venpy generate '.out' file?
- Replies: 2
- Views: 2976
Re: Does running Powell using DLL/Venpy generate '.out' file?
The output should be the same. We'll have to take a look. Do you have a test case?
- Thu May 29, 2025 4:55 pm
- Forum: Vensim
- Topic: MCMC with multiple chains and starting points
- Replies: 3
- Views: 2872
Re: MCMC with multiple chains and starting points
One way to assess what's going on is to look at the _distrib file that gets generated. If you filter out the final sample and plot a parameter against iteration, you can see how the distribution evolves.
- Wed May 28, 2025 6:38 pm
- Forum: Vensim
- Topic: MCMC with multiple chains and starting points
- Replies: 3
- Views: 2872
Re: MCMC with multiple chains and starting points
No. There are three initialization methods: overdisperse, underdisperse, and hybrid (set by the MCINIT parameter). - over draws in the same way Powell multistart works, from a very broad powerlaw distribution (or uniform if both bounds are set); in the future, I'd like to modify this to draw from yo...
- Wed May 28, 2025 3:42 pm
- Forum: Vensim
- Topic: Modeling simultaneous substitution flows
- Replies: 3
- Views: 5134
Re: Modeling simultaneous substitution flows
I'm puzzled by your statement that "defining simultaneous flows in two directions unintentionally inflates total demand. For example, demand moves from Brand B to Brand A, and then flows back to Brand B." In your example, demand is conserved. If demand shifts from A to B, the demand for B ...
- Wed May 28, 2025 3:33 pm
- Forum: Vensim
- Topic: connectors to vars scrolled to not possible
- Replies: 3
- Views: 2678
Re: connectors to vars scrolled to not possible
Here's a possible workaround: Edit the equation for the destination variable. Add the source variable to the expression. When you exit, accept the request to add the source connection to the diagram. At this point, you'll have a straight arrow from source->destination. Navigate to the midpoint and c...
- Mon May 26, 2025 11:52 pm
- Forum: Vensim
- Topic: How to rea-add part of a flow?
- Replies: 2
- Views: 4214
Re: How to rea-add part of a flow?
I think it's possible - use the flow tool to click on the valve, then click on the target (whitespace for a cloud, or another stock). You may have an unwanted arrowhead at this point, which you can turn off with a right-click.
- Thu May 22, 2025 7:34 pm
- Forum: Vensim
- Topic: two constants as input, with a time delay on one constant
- Replies: 2
- Views: 3399
Re: two constants as input, with a time delay on one constant
Maybe this?
glucose in = infusion + endogenous
endogenous = STEP( endogenous rate, endogenous start time )
endogenous start time = 2
infusion = STEP( infusion rate, endogenous start time + infusion delay )
infusion delay = 4
glucose in = infusion + endogenous
endogenous = STEP( endogenous rate, endogenous start time )
endogenous start time = 2
infusion = STEP( infusion rate, endogenous start time + infusion delay )
infusion delay = 4
- Mon May 19, 2025 2:42 pm
- Forum: Vensim
- Topic: Help with Vensim
- Replies: 3
- Views: 3839
Re: Help with Vensim
There are also some video courses here https://vensim.com/video/