Search found 2041 matches

by tomfid
Tue Dec 12, 2017 3:38 pm
Forum: Ventity
Topic: Problem with using different datasets for same model
Replies: 2
Views: 55

Re: Problem with using different datasets for same model

Are these initialization datasets, or time series?
by tomfid
Tue Dec 12, 2017 2:45 pm
Forum: Vensim
Topic: Secondary Y axis in custom graph
Replies: 3
Views: 46

Re: Secondary Y axis in custom graph

You can have 2 scales, but they appear together on the left. They're useful for a modeler who knows what's going on, but I wouldn't recommend it for general consumption.
by tomfid
Mon Dec 11, 2017 3:53 pm
Forum: Vensim
Topic: List of variables to change values for simulation in single screen
Replies: 6
Views: 22

Re: List of variables to change values for simulation in single screen

For running scenarios, you should not edit equations. Instead, use constant changes files, the constant settings in the simulation control dialog, or Synthesim to make temporary changes. That preserves the integrity of your model much better. The diagram difference is indicating exactly what you hav...
by tomfid
Mon Dec 11, 2017 3:33 pm
Forum: Vensim
Topic: List of variables to change values for simulation in single screen
Replies: 6
Views: 22

Re: List of variables to change values for simulation in single screen

Or use the Model Constants button when you're in Sim Setup mode.
by tomfid
Fri Dec 08, 2017 4:05 pm
Forum: Vensim
Topic: How can I use Vensim DLL in Python, Linux?
Replies: 8
Views: 910

Re: How can I use Vensim DLL in Python, Linux?

Forio.com runs on the MC library on Linux, as do several other high-traffic simulations.
by tomfid
Wed Dec 06, 2017 4:43 pm
Forum: Vensim
Topic: Excel file as an input for a lookup
Replies: 7
Views: 40

Re: Excel file as an input for a lookup

Specifically, the Help includes a sample model for every built in function, including the GET XLS variants. Sometimes the OS will lock out the links, but you can also find them in the Vensim folder (usually C:\users\public\vensim on Windows).
by tomfid
Wed Dec 06, 2017 3:15 am
Forum: Vensim
Topic: How to set extremely low stock to be exactly zero and ensure reasonable co-flow results?
Replies: 1
Views: 44

Re: How to set extremely low stock to be exactly zero and ensure reasonable co-flow results?

I'm not sure there's a good general solution that's problem-independent, other than switching to double precision Vensim DSS.

What's your use case for this?
by tomfid
Tue Dec 05, 2017 5:22 pm
Forum: Vensim
Topic: Subscript reshape (stitching)
Replies: 4
Views: 30

Re: Subscript reshape (stitching)

I was close. See attached.

halfhour datetime.mdl
(15.91 KiB) Downloaded 3 times
by tomfid
Tue Dec 05, 2017 4:20 pm
Forum: Vensim
Topic: Subscript reshape (stitching)
Replies: 4
Views: 30

Re: Subscript reshape (stitching)

I think VECTOR ELM MAP might be the easiest way to do this. First you want to pre-calculate the mappings: HalfHr of DateTime[D,T] = INITIAL( (D-1)*ELMCOUNT(T) + T-1 ) DateTime of HalfHr[HH] = INITIAL( HH-1 ) Note the -1, because VECTOR ELM MAP uses zero-based arrays, but subscript values are one-bas...
by tomfid
Mon Dec 04, 2017 3:10 pm
Forum: Vensim
Topic: Save sensitivity graph as .vgd
Replies: 2
Views: 40

Re: Save sensitivity graph as .vgd

You can't save the graph directly to vgd, but you can construct one in a vgd - see the CONFIDENCE and SENS-LINES keywords:
https://www.vensim.com/documentation/index.html?23930.htm
by tomfid
Mon Dec 04, 2017 1:44 am
Forum: Vensim
Topic: Cap for multiple outflows to avoid negative stock
Replies: 2
Views: 50

Re: Cap for multiple outflows to avoid negative stock

The solution depends on the logic of the situation. Tony's approach works when there's a natural prioritization. Another possibility is something like this: Desired Outflow = Desired A out + Desired B out Max Outflow = Stock/Min Time to Drain Min Time to Drain >= TIME STEP Total Outflow = MIN( Desir...
by tomfid
Wed Nov 29, 2017 11:34 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 356
Views: 9854

Re: Help with model calibration

Right.
by tomfid
Wed Nov 29, 2017 5:21 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 356
Views: 9854

Re: Help with model calibration

I think this could be made quite easy in Vensim. - Create a flag for each driver, indicating whether treatment was received (a constant) or when it was received (time series) - Import the data for ALL drivers - Rewrite "fraction perceived" as something like = IF THEN ELSE( treatment, 1, ba...
by tomfid
Wed Nov 29, 2017 3:33 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 356
Views: 9854

Re: Help with model calibration

I thought your initial event rate parameter had [driver] detail, so that the mean for every driver was centered? Because the experimental design doesn't randomly assign the treatment, any conclusion about differences between the two groups is pretty speculative. One could always argue that the high-...
by tomfid
Wed Nov 29, 2017 3:16 pm
Forum: Ventity
Topic: Market action
Replies: 4
Views: 93

Re: Market action

There is indeed a bug. We're working on it.
by tomfid
Wed Nov 29, 2017 5:30 am
Forum: Vensim
Topic: Help with model calibration
Replies: 356
Views: 9854

Re: Help with model calibration

Understood. I think the short answer is "yes" - should be possible to account for this in Vensim. I'm traveling tomorrow but will answer as I can.
by tomfid
Wed Nov 29, 2017 12:43 am
Forum: Vensim
Topic: Help with model calibration
Replies: 356
Views: 9854

Re: Help with model calibration

Something is definitely amiss if the simulated and real means differ by this much.
by tomfid
Tue Nov 28, 2017 11:52 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 356
Views: 9854

Re: Help with model calibration

Not sure what you mean by "offset" - delay?
by tomfid
Tue Nov 28, 2017 10:29 pm
Forum: Vensim
Topic: Limit of number of variables included in a custom graph
Replies: 2
Views: 45

Re: Limit of number of variables included in a custom graph

You can put more than 6 if you export the graph set to .vgd and edit it with a text editor, I think.
by tomfid
Tue Nov 28, 2017 9:10 pm
Forum: Ventity
Topic: Debugging problem
Replies: 2
Views: 42

Re: Debugging problem

I think this must be fixed in our current builds. I'll send you a link for the latest 1.2 release candidate. The real release should be any day now.
by tomfid
Tue Nov 28, 2017 4:38 pm
Forum: Vensim
Topic: Simulation outside of the range of the data
Replies: 3
Views: 56

Re: Simulation outside of the range of the data

The trouble with :RAW: data is that it's easy to forget that you've used the keyword, and then your model gets an occasional spurious :NA: that wrecks things. When we use it, we often create a copy, like: real data := GET XLS DATA( blabla ) raw data :RAW: := real data That way it's harder to get mix...
by tomfid
Mon Nov 27, 2017 10:15 pm
Forum: Vensim
Topic: Simulation outside of the range of the data
Replies: 3
Views: 56

Re: Simulation outside of the range of the data

I think you need two things: 1. For the data conversion, use a data equation rather than a regular equation. This preserves the "emptiness" of missing data. Something like: distance M := distance in / in per M 2. For the forecast, use an IF THEN ELSE to set it to NA before it becomes activ...
by tomfid
Mon Nov 27, 2017 3:05 pm
Forum: Ventity
Topic: Market action
Replies: 4
Views: 93

Re: Market action

We're back from the holiday and will take a look.
by tomfid
Sun Nov 26, 2017 2:21 pm
Forum: Vensim
Topic: Silly question
Replies: 4
Views: 85

Re: Silly question

As a workaround, you could add a converter for watts per joule/sec, and use that in places where it's convenient to make the transition.
by tomfid
Sat Nov 25, 2017 7:06 pm
Forum: Vensim
Topic: Silly question
Replies: 4
Views: 85

Re: Silly question

Afraid not. We should add that. Ventity does it.

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