Right ... it's (775,000-433,000) people/year for 1/8 year in the first time step, so the expected change is 43,000 - which is what you get.
With Euler integration:
stock(t+dt) = stock(t) + (inflow-outflow)*dt
with units
people = people + (people/year)*year
where dt = time step = .0125
Search found 3811 matches
- Thu Jun 12, 2014 2:13 pm
- Forum: Vensim
- Topic: Shift if true.mdl
- Replies: 8
- Views: 4234
- Wed Jun 11, 2014 9:43 pm
- Forum: Vensim
- Topic: Shift if true.mdl
- Replies: 8
- Views: 4234
Re: Shift if true.mdl
There may be a bug in SHIFT IF TRUE in your version - I get the expected decrease of about 500/yr when I run with 6.3. Time for a maintenance extension - 5.0 is ten years old!
- Wed Jun 11, 2014 9:31 pm
- Forum: Vensim
- Topic: Shift if true.mdl
- Replies: 8
- Views: 4234
Re: Shift if true.mdl
Here's a model with a checksum that is what I'd expect from your description. There are slight numerical discrepancies - about .01% - presumably due to roundoff. Nothing like what you're describing. As an extra check, the final population should be 172.5M when you run this.
- Tue Jun 10, 2014 6:44 pm
- Forum: Vensim
- Topic: Vensim 6.3 released
- Replies: 0
- Views: 4317
Vensim 6.3 released
See http://vensim.com/vensim-6-3-released/ for details & downloads.
- Mon Jun 09, 2014 5:32 pm
- Forum: Vensim
- Topic: Gaming with subscripts
- Replies: 12
- Views: 7170
Re: Gaming with subscripts
I think the error persists because "error" is in some of the subscript definition fields. How it got there in the first place appears to be a bug in the Add Subscripts menu command. However, the bug only occurs when subscripts are added to a particularly anomalous model, like the original ...
- Mon Jun 09, 2014 3:25 pm
- Forum: Vensim
- Topic: PULSE TRAIN function
- Replies: 2
- Views: 2251
Re: PULSE TRAIN function
Right - there's a sample model in the help system that illustrates this. http://www.vensim.com/documentation/fn_pulse_train.htm
- Fri Jun 06, 2014 4:49 pm
- Forum: Vensim
- Topic: Gaming with subscripts
- Replies: 12
- Views: 7170
Re: Gaming with subscripts
Try starting from this:
- Fri Jun 06, 2014 4:45 pm
- Forum: Vensim
- Topic: Gaming with subscripts
- Replies: 12
- Views: 7170
Re: Gaming with subscripts
I can replicate the varformat error. But it seems that the original model is not in a working state, prior to attempting to add the subscript. Many of the variables are defined as data, and therefore are missing their equations.
- Fri Jun 06, 2014 4:09 pm
- Forum: Vensim
- Topic: Error: Gaming file corrupted
- Replies: 3
- Views: 2341
Re: Error: Gaming file corrupted
Also, is this a venapp, or just a model? If the latter, the first places I'd look would be (a) the simulation control dialog (Model>Simulate menu), Changes tab, Based On field, (b) simulation control Advanced tab, Data Sources field, and (c) the filename passed in GET VDF functions in the equations,...
- Wed Jun 04, 2014 11:57 pm
- Forum: Vensim
- Topic: Vensim and xmile
- Replies: 2
- Views: 2129
Re: Vensim and xmile
BTW, what's your interest here? Migrating a few big models? Browsing models across platforms? ... ? (We're curious because it affects how we prioritize different aspects of the implementation.)
- Wed Jun 04, 2014 9:36 pm
- Forum: Vensim
- Topic: Vensim and xmile
- Replies: 2
- Views: 2129
Re: Vensim and xmile
Not yet. We do plan to support it at some point, but we've been too busy working on new tools.
- Thu May 15, 2014 6:38 pm
- Forum: Vensim
- Topic: How to Solve error comes???
- Replies: 2
- Views: 2043
Re: How to Solve error comes???
The general strategy here is to plug in the parameters reported as causing the error,
and run an ordinary simulation to see what the error is.
Code: Select all
R1 = 0.397753
R5 = 0.196305
R10 = 0.475031
W = 0.203637
- Thu May 08, 2014 9:44 pm
- Forum: Vensim
- Topic: need help.inputting data from excel file
- Replies: 1
- Views: 1532
- Mon Apr 28, 2014 9:30 pm
- Forum: Vensim
- Topic: Base Variable on the Graph (Venapp)
- Replies: 11
- Views: 4739
Re: Base Variable on the Graph (Venapp)
If that's not it, I think I'd have to see an example.
- Mon Apr 28, 2014 9:29 pm
- Forum: Vensim
- Topic: Base Variable on the Graph (Venapp)
- Replies: 11
- Views: 4739
Re: Base Variable on the Graph (Venapp)
No - but one thing to check is whether you inadvertently exited without saving your analysis toolbar settings - you may be back to "Selected Vars" on the graph tool.
- Mon Apr 28, 2014 2:08 pm
- Forum: Vensim
- Topic: Can Lookups deal with variables in the output
- Replies: 3
- Views: 3996
Re: Can Lookups deal with variables in the output
This can be done with VECTOR LOOKUP - http://www.vensim.com/documentation/fn_ ... lookup.htm
- Fri Apr 25, 2014 1:54 am
- Forum: Vensim
- Topic: Base Variable on the Graph (Venapp)
- Replies: 11
- Views: 4739
Re: Base Variable on the Graph (Venapp)
I think this may be a bug - we'll have to investigate - but I think something goes wrong when the "Selected Vars" option is checked in the graph tool. Try right-clicking your graph tool in the analysis toolbar and unchecking that setting (near bottom left).
- Wed Apr 23, 2014 3:50 am
- Forum: Vensim
- Topic: Running a model in hours, keeping track of days....
- Replies: 4
- Views: 5145
Re: Running a model in hours, keeping track of days....
One strategy to think about, somewhat common in electric power modeling, would be to simulate only representative times per day or days per month/season. You could also potentially move some of the hourly detail off the time axis and into an array dimension, if serial correlation isn't a big deal.
- Tue Apr 22, 2014 1:32 pm
- Forum: Vensim
- Topic: Base Variable on the Graph (Venapp)
- Replies: 11
- Views: 4739
Re: Base Variable on the Graph (Venapp)
Are you actually developing a model with graphs on the diagrams, using the Input/Output object with a workbench variable? (If so, I think I may know what's happening.)
- Tue Apr 22, 2014 1:29 pm
- Forum: Vensim
- Topic: Problem with Vensim
- Replies: 3
- Views: 2111
Re: Problem with Vensim
If you can send us a copy of the model, we might be able to track it down. We haven't changed anything in the diagramming that I'm aware of.
- Mon Apr 14, 2014 1:07 pm
- Forum: Vensim
- Topic: Can't figure out how weight and payoff work in calibration
- Replies: 7
- Views: 4746
Re: Can't figure out how weight and payoff work in calibrati
If your errors are normally distributed and the payoff is properly weighted according to the standard errors, the expected value of the payoff is the number of data points.
Also, check the payoff report (*.rep file) for additional diagnostic stats.
Also, check the payoff report (*.rep file) for additional diagnostic stats.
- Mon Apr 07, 2014 1:03 pm
- Forum: Vensim
- Topic: Subscripts
- Replies: 2
- Views: 2315
Re: Subscripts
That's the right syntax. What do you mean by "not working" ?
- Sun Apr 06, 2014 2:51 am
- Forum: Vensim
- Topic: about floating error
- Replies: 4
- Views: 2563
Re: about floating error
When a model has explosive floating point errors like this, it's generally useful to re-run it for a short time (like 2014-2018 in this case) to make it easier to see what's going on. Also, if you're using an advanced version, right-click the Table tool and set it to show "Causes" rather t...
- Tue Apr 01, 2014 12:33 am
- Forum: Vensim
- Topic: type of distribution for sensitivity analysis
- Replies: 2
- Views: 1780
Re: type of distribution for sensitivity analysis
You can often transform a UNIFORM variable to the needed distribution, for example:
http://en.wikipedia.org/wiki/Fr%C3%A9ch ... tributions
http://en.wikipedia.org/wiki/Fr%C3%A9ch ... tributions
- Tue Apr 01, 2014 12:31 am
- Forum: Vensim
- Topic: Approaches for Different Units by Subscript Value?
- Replies: 2
- Views: 1972
Re: Approaches for Different Units by Subscript Value?
I think your solution is about as good as it gets, unfortunately. Will ponder...