Search found 3811 matches
- Sun Apr 21, 2024 1:22 pm
- Forum: Vensim
- Topic: Integration techniques: Impacts on Stock behavior
- Replies: 5
- Views: 194
Re: Integration techniques: Impacts on Stock behavior
I think Aliakhavan89 is on the right track. However, it's impossible to give a precise answer without more information than the chart provides. What are the TIME STEP and SAVEPER? Presumably 12000 hours from eyeballing the chart? What is the equation for end use efficiency? A step * exponential? Or ...
- Sun Apr 21, 2024 1:12 pm
- Forum: Vensim
- Topic: Death by Subscript
- Replies: 5
- Views: 122
Re: Death by Subscript
SUM is definitely the summation operator Sigma. The exclamation point is not useless; it is necessary in cases where you'd like to sum over a subset of the dimensions belonging to the right side. I would write the equation in your image with something like the following: n : n1, n2 s : <something> a...
- Sat Apr 20, 2024 11:27 pm
- Forum: Vensim
- Topic: Death by Subscript
- Replies: 5
- Views: 122
Re: Death by Subscript
Looking at the model may not be required, but I'm not sure an answer can be given from the material here. What you're showing seems syntactically valid, so the problem may be somewhere else. What are the definitions of h and pressure number? What is on the left side of the sum expression? Is h the e...
- Sun Apr 14, 2024 9:49 pm
- Forum: Vensim
- Topic: SINTEG with vars
- Replies: 4
- Views: 114
Re: SINTEG with vars
Probably not, but you could modify your flow equations to do the same thing. We'd have to have a concrete example to comment on.
- Mon Apr 01, 2024 2:23 pm
- Forum: Vensim
- Topic: two imodels with no significant differences behaving differently
- Replies: 2
- Views: 112
Re: two imodels with no significant differences behaving differently
#2 has the Simulate>Based On setting active, which might change the lookup.
- Thu Mar 28, 2024 6:17 pm
- Forum: Vensim
- Topic: double-click selection
- Replies: 5
- Views: 2688
Re: double-click selection
Some of this will change with the new equation editor soon.
- Thu Mar 28, 2024 6:16 pm
- Forum: Vensim
- Topic: How to calculate the difference in value for a variable in vensim over time?
- Replies: 2
- Views: 1272
Re: How to calculate the difference in value for a variable in vensim over time?
You can use DELAY FIXED for this: Previous GDP = DELAY FIXED( Current GDP, one year, Current GDP ) ~ $/year one year == 1 ~ year In continuous time, you can use the SMOOTH function, i.e. Previous GDP = SMOOTH( Current GDP, one year ) ~ $/year You can also use the TREND function to compute a fraction...
- Thu Mar 21, 2024 1:11 am
- Forum: Vensim
- Topic: it is frustrating!
- Replies: 25
- Views: 3516
Re: it is frustrating!
Is the run "current" the first loaded dataset?
- Thu Mar 21, 2024 1:10 am
- Forum: Vensim
- Topic: Continuos or discrete variables?
- Replies: 4
- Views: 1918
Re: Continuos or discrete variables?
On the other hand, if you're interested in stochastic extinction of a disease in a small population, integer values may matter.
It's impossible to answer these questions in general; some specifics of the question to be answered must be known.
It's impossible to answer these questions in general; some specifics of the question to be answered must be known.
- Thu Mar 21, 2024 1:08 am
- Forum: Vensim
- Topic: Continuos or discrete variables?
- Replies: 4
- Views: 1918
Re: Continuos or discrete variables?
Like Forrester, I think that discrete quantities are rarely a good place to start. Things that are theoretically only available in integer quantities either don't matter, or have qualifications. For example, people are certainly available in integer quantities. But what about the work-equivalent of ...
- Thu Mar 21, 2024 1:04 am
- Forum: Vensim
- Topic: Continuos or discrete variables?
- Replies: 4
- Views: 1918
- Fri Mar 08, 2024 3:57 pm
- Forum: Vensim
- Topic: Help with PULSE TRAIN and random variable
- Replies: 6
- Views: 1822
Re: Help with PULSE TRAIN and random variable
Try this instead ...
You can also use SAMPLE IF TRUE for this (though I think it's not available in all versions).
You can also use SAMPLE IF TRUE for this (though I think it's not available in all versions).
- Tue Mar 05, 2024 2:06 pm
- Forum: Vensim
- Topic: it is frustrating!
- Replies: 25
- Views: 3516
- Mon Mar 04, 2024 4:36 pm
- Forum: Vensim
- Topic: where is the sim set up from the old GUI in the new one?
- Replies: 9
- Views: 17631
Re: where is the sim set up from the old GUI in the new one?
Not sure I'm tracking the issue here. In the old gui, PLE sim setup doesn't have a dialog. Everything is in the toolbar. 2024-03-04_09-33-54.png In the new gui, PLE does have a dialog (albeit without much content). 2024-03-04_09-32-44.png In both cases, constants and lookups are highlighted, and you...
- Mon Feb 05, 2024 11:10 pm
- Forum: Vensim
- Topic: Reinstall Vensim (error 977).
- Replies: 5
- Views: 996
Re: Reinstall Vensim (error 977).
Typically this indicates a path problem. Have you moved the dll?
- Fri Feb 02, 2024 4:00 pm
- Forum: Vensim
- Topic: RC Fonksiyon
- Replies: 1
- Views: 780
Re: RC Fonksiyon
I think you'll have to elaborate a bit, because there are a lot of different possible population structures, which might call for different approaches.
One option is to use the Little's Law equilibrium estimate, i.e. residence time = stock/flow_throughput. https://en.wikipedia.org/wiki/Little%27s_law
One option is to use the Little's Law equilibrium estimate, i.e. residence time = stock/flow_throughput. https://en.wikipedia.org/wiki/Little%27s_law
- Fri Feb 02, 2024 2:00 pm
- Forum: System Dynamics Discussion
- Topic: Utilizing Ventana Systems Tools for enhancing data breach protection strategies ?
- Replies: 3
- Views: 2435
Re: Utilizing Ventana Systems Tools for enhancing data breach protection strategies ?
For starters, google "sander zeijlemaker security system dynamics" - he's done quite a bit of interesting work. You should be able to find much of it in the ISDC conference proceedings.
- Fri Feb 02, 2024 1:52 pm
- Forum: Vensim
- Topic: Can the Vensim PLE version achieve seasonal forecasting?
- Replies: 2
- Views: 908
Re: Can the Vensim PLE version achieve seasonal forecasting?
I think the month variable is intentional, for creating a seasonal input.
Since the seasonal behavior has 3 episodes, switched in an IF THEN ELSE statement, I think you could create the same thing for seasonal smoothing - have 3 smoothing structures, one active during each episode.
Since the seasonal behavior has 3 episodes, switched in an IF THEN ELSE statement, I think you could create the same thing for seasonal smoothing - have 3 smoothing structures, one active during each episode.
- Thu Feb 01, 2024 3:45 pm
- Forum: Vensim
- Topic: Units tips or laws
- Replies: 7
- Views: 1330
Re: Units tips or laws
Your flows are dimensioned dmnl/hour, but your time unit in Model>Settings is Mes.
- Wed Jan 31, 2024 3:57 pm
- Forum: Vensim
- Topic: Units tips or laws
- Replies: 7
- Views: 1330
Re: Units tips or laws
There are at least two rules: - a flow has the same units as the stock it connects to, divided by the time unit - EXP, LN, and a number of other functions require dimensionless units beyond that, if you have y = a / b the units follow y units = a units/b units One consequence of this is that you can...
- Mon Jan 29, 2024 6:30 pm
- Forum: Vensim
- Topic: Copy & Paste between models
- Replies: 4
- Views: 2206
Re: Copy & Paste between models
If you open them in the same application instance, this works. (If you open the files by double-clicking from the finder/explorer, you have two application instances, and it won't work.)
In pro/DSS, general settings, you can enable opening multiple models simultaneously.
In pro/DSS, general settings, you can enable opening multiple models simultaneously.
- Thu Jan 25, 2024 5:35 pm
- Forum: Vensim
- Topic: Max file size
- Replies: 5
- Views: 1469
Re: Max file size
I think the 3221226505 return code may be a variable type mismatch - this has been reported in other contexts.
- Sun Jan 14, 2024 11:19 pm
- Forum: Vensim
- Topic: Finding MAX of simulation variable
- Replies: 2
- Views: 1519
Re: Finding MAX of simulation variable
If you can make the calculation at FINAL TIME, you can use SAMPLE IF TRUE to hold the max value over the simulation - there's an example in the help system.
- Wed Jan 10, 2024 5:44 pm
- Forum: Vensim
- Topic: Get data xls with multiple subscripts
- Replies: 4
- Views: 6701
Re: Get data xls with multiple subscripts
In a case like this, importing the data to vdf would be less error-prone.
- Wed Jan 10, 2024 5:42 pm
- Forum: Vensim
- Topic: Get data xls with multiple subscripts
- Replies: 4
- Views: 6701
Re: Get data xls with multiple subscripts
The GET DATA calls are basically 1-dimensional because the spreadsheet is 2D, and one is taken by time.
One possible way to semi-automate a GET call with more dimensions is to put the sheet names or first-cell references in a string variable with the appropriate subscripting.
One possible way to semi-automate a GET call with more dimensions is to put the sheet names or first-cell references in a string variable with the appropriate subscripting.