Search found 3815 matches
- Mon Jul 31, 2023 7:19 pm
- Forum: Vensim
- Topic: how do I reload an existing dataset, including variable values?
- Replies: 5
- Views: 590
- Mon Jul 31, 2023 6:14 pm
- Forum: Vensim
- Topic: how do I reload an existing dataset, including variable values?
- Replies: 5
- Views: 590
Re: how do I reload an existing dataset, including variable values?
If you change variable values interactively, e.g. by moving sliders, the model always retains the underlying equation values as a default. If you change the equations, you have to manually change back. More advanced versions of Vensim can save and load change files (.cin) during simulations, to make...
- Mon Jul 31, 2023 6:07 pm
- Forum: Vensim
- Topic: Units Check whack-a-mole
- Replies: 9
- Views: 1212
Re: Units Check whack-a-mole
After a closer look, my conclusion is that the model is kind of bonkers. Normally units prevent conceptual errors like mixing up stocks and flows, but in this case I think the general difficulty in defining units is a big red flag in itself. It means that the model is rather far from an operational ...
- Mon Jul 31, 2023 4:36 pm
- Forum: Vensim
- Topic: Model calibration in Vensim PLE
- Replies: 2
- Views: 530
Re: Model calibration in Vensim PLE
No - PLE is really targeted at learning about dynamics.
- Sun Jul 30, 2023 7:25 pm
- Forum: Vensim
- Topic: how do I reload an existing dataset, including variable values?
- Replies: 5
- Views: 590
Re: how do I reload an existing dataset, including variable values?
Rather than editing equations, you probably want to make your changes to the model live, in Synthesim, or using change files.
- Sun Jul 30, 2023 1:10 am
- Forum: Vensim
- Topic: Units Check whack-a-mole
- Replies: 9
- Views: 1212
Re: Units Check whack-a-mole
I'll take a look in greater depth Monday, but I tend to agree that these errors reflect some conceptual issues with the model. I find the rewilding equation extremely weird. I'd probably fix the units by adding an explicit parameter, with value 1, to make clear that there's an implicit conversion go...
- Sun Jul 30, 2023 12:57 am
- Forum: Vensim
- Topic: Reverse engineering
- Replies: 3
- Views: 550
Re: Reverse engineering
Generally a causal loop diagram can't be translated automatically to a model, because it simply doesn't contain enough information. The COIN diagram you posted actually has an underlying model that is much larger. https://metasd.com/2010/04/hypnotizing-chickens/ You should be able to turn a CLD into...
- Fri Jul 28, 2023 9:46 pm
- Forum: Vensim
- Topic: Units Check whack-a-mole
- Replies: 9
- Views: 1212
Re: Units Check whack-a-mole
A stock equation is the integral of a flow over time, so the stock unit has the flow unit * time unit. This is easier to see if you write the discrete update that happens with Euler integration: stock(t+dt) = stock(t) + dt*(inflows-outflows) were t=time, dt=TIME STEP in Vensim. This has units: stock...
- Fri Jul 28, 2023 9:19 pm
- Forum: Vensim
- Topic: Input Mode
- Replies: 2
- Views: 487
Re: Input Mode
I'm not sure what you mean by "input mode".
The conventional way to implement exponential growth is:
stock = INTEG( - outflow, initial stock ) ~ stuff
outflow = stock * loss rate ~ stuff/time
or
outflow = stock / lifetime
The conventional way to implement exponential growth is:
stock = INTEG( - outflow, initial stock ) ~ stuff
outflow = stock * loss rate ~ stuff/time
or
outflow = stock / lifetime
- Fri Jul 28, 2023 9:19 pm
- Forum: Vensim
- Topic: Input Mode
- Replies: 2
- Views: 487
Re: Input Mode
I'm not sure what you mean by "input mode".
The conventional way to implement exponential growth is:
stock = INTEG( - outflow, initial stock ) ~ stuff
outflow = stock * loss rate ~ stuff/time
or
outflow = stock / lifetime
The conventional way to implement exponential growth is:
stock = INTEG( - outflow, initial stock ) ~ stuff
outflow = stock * loss rate ~ stuff/time
or
outflow = stock / lifetime
- Fri Jul 28, 2023 2:38 am
- Forum: Vensim
- Topic: Units Check whack-a-mole
- Replies: 9
- Views: 1212
Re: Units Check whack-a-mole
The Log(Pop) error can be handled by defining something like unit pop == 1 ~ person and then normalizing logpop = log( pop/unit pop + 1 ) The other two errors seem like a unit problem with knowledge. Flows always have units of their associated stock, divided by the time unit. Therefore if learning a...
- Thu Jul 27, 2023 5:01 am
- Forum: Vensim
- Topic: Exogenous data in transportation model
- Replies: 8
- Views: 1396
Re: Exogenous data in transportation model
PLE doesn't include the stats tool unfortunately. You could generate a table and copy/paste to Excel or something for the comparison.
- Thu Jul 27, 2023 4:58 am
- Forum: Vensim
- Topic: The use of 'TIME STEP' in equations
- Replies: 8
- Views: 741
Re: The use of 'TIME STEP' in equations
However ... the TREND function does essentially what I proposed, without requiring the extra equation.
- Tue Jul 25, 2023 9:43 pm
- Forum: Vensim
- Topic: The use of 'TIME STEP' in equations
- Replies: 8
- Views: 741
Re: The use of 'TIME STEP' in equations
It sounds like you're trying to recover the value of a variable at a previous time step? This appears to be computing a growth rate or derivative? You could write something like: Previous Resident Income = SMOOTH(Resident Income,TIME STEP) income trend = ( (Resident Income - Previous Resident Income...
- Mon Jul 24, 2023 1:22 am
- Forum: Vensim
- Topic: Response Time
- Replies: 0
- Views: 10040
Response Time
Many of us are at #ISDC2023 so response times will be longer this week.
- Mon Jul 24, 2023 1:10 am
- Forum: Vensim
- Topic: a simple example of my gnarly IF THEN ELSE problem (bug?)
- Replies: 8
- Views: 706
Re: a simple example of my gnarly IF THEN ELSE problem (bug?)
Correct - no - because then there would be no value to assign to the LHS.
- Mon Jul 24, 2023 1:08 am
- Forum: Vensim
- Topic: a gnarly IF THEN ELSE problem
- Replies: 9
- Views: 1052
Re: a gnarly IF THEN ELSE problem
Your translation has two clauses for # if false that Time-sy <= 0 - you can get rid of the second q = 1 ), Then it can be implemented as q = IF THEN ELSE( pE < w , {# if true that pE < w} IF THEN ELSE( Time-sy <= 0 , {# if true that Time-sy <= 0} {q =} 1 , {# if false that Time-sy <= 0} IF THEN ELSE...
- Mon Jul 24, 2023 12:32 am
- Forum: Vensim
- Topic: a simple example of my gnarly IF THEN ELSE problem (bug?)
- Replies: 8
- Views: 706
Re: a simple example of my gnarly IF THEN ELSE problem (bug?)
The only assignment in Vensim is to the left hand side variable. If you want to make multiple assignments, you can use distinct variables, or subscript elements. You can't make multiple assignments within a single equation.
- Mon Jul 24, 2023 12:28 am
- Forum: Vensim
- Topic: a gnarly IF THEN ELSE problem
- Replies: 9
- Views: 1052
Re: a gnarly IF THEN ELSE problem
The Vensim language doesn't support that kind of procedural code. I'm not sure it improves readability over nesting.
- Sun Jul 23, 2023 7:33 pm
- Forum: Vensim
- Topic: Start new models failed
- Replies: 15
- Views: 1103
Re: Start new models failed
I hope this means it's working?
- Sun Jul 23, 2023 7:31 pm
- Forum: Vensim
- Topic: a gnarly IF THEN ELSE problem
- Replies: 9
- Views: 1052
Re: a gnarly IF THEN ELSE problem
I think your simplification is incorrect, because it doesn't nest. It should look li
IF THEN ELSE( a=b, c
, IF THEN ELSE( d=e, f, g)
)
IF THEN ELSE( a=b, c
, IF THEN ELSE( d=e, f, g)
)
- Sun Jul 23, 2023 7:27 pm
- Forum: Vensim
- Topic: a simple example of my gnarly IF THEN ELSE problem (bug?)
- Replies: 8
- Views: 706
Re: a simple example of my gnarly IF THEN ELSE problem (bug?)
This kind of looks like procedural code in the equation field. You can't do that, by design.
100
c*d
is read as
100 c*d
(after condensing the whitespace).
This would have to be
100 <operator> c*d
where <operator> is + - * / ^ in order to make sense.
100
c*d
is read as
100 c*d
(after condensing the whitespace).
This would have to be
100 <operator> c*d
where <operator> is + - * / ^ in order to make sense.
- Sun Jul 23, 2023 7:17 pm
- Forum: Vensim
- Topic: Start new models failed
- Replies: 15
- Views: 1103
Re: Start new models failed
We split it into two ... won't update the video until later, because there's a big update for these tools in the pipeline.
- Fri Jul 21, 2023 2:22 pm
- Forum: Vensim
- Topic: Start new models failed
- Replies: 15
- Views: 1103
Re: Start new models failed
Not having seen this before, I'm pretty stumped. When the pred-prey model opened, could you interact with it? "PL9999" is the standard s/n for all academic PLE, so unfortunately that doesn't provide a clue. Long shot, but anything unusual about the environment? (multiple monitors, remote a...
- Fri Jul 21, 2023 1:33 pm
- Forum: Vensim
- Topic: Exporting large sensitivity output
- Replies: 2
- Views: 472
Re: Exporting large sensitivity output
You could use a savelist or SAVEPER to reduce the scale of the data.
You could also try the relational Data List format or .dat (though the latter is not really friendly to other apps). Both will be large.
.tab is probobly no better, and .xls is surely worse.
You could also try the relational Data List format or .dat (though the latter is not really friendly to other apps). Both will be large.
.tab is probobly no better, and .xls is surely worse.