Search found 3048 matches

by tomfid
Fri Sep 25, 2020 5:21 pm
Forum: Vensim
Topic: SD models like C-ROAD
Replies: 4
Views: 14

Re: SD models like C-ROAD

Vensim can now publish web simulations, but does not yet support external data.

I think your best option as of today is SDE or Forio.
by tomfid
Fri Sep 18, 2020 2:55 pm
Forum: Vensim
Topic: New Sketch leads to weird menu state
Replies: 1
Views: 32

Re: New Sketch leads to weird menu state

Investigating...
by tomfid
Thu Sep 17, 2020 1:44 pm
Forum: Vensim
Topic: Sensitivity Graph Y-Axis Range
Replies: 10
Views: 76

Re: Sensitivity Graph Y-Axis Range

Neither - this would be a cmd script within Vensim, which requires DSS.
by tomfid
Wed Sep 16, 2020 9:37 pm
Forum: Vensim
Topic: Sensitivity Graph Y-Axis Range
Replies: 10
Views: 76

Re: Sensitivity Graph Y-Axis Range

Also, you actually can export sensitivity data with confidence bounds, using a cmd script and SENS2FILE with the % key - https://www.vensim.com/documentation/sens2file.htm
by tomfid
Wed Sep 16, 2020 1:11 pm
Forum: Vensim
Topic: Moving average
Replies: 2
Views: 2002

Re: Moving average

For many purposes it is both much easier and more realistic to use an exponentially-weighted moving average via the SMOOTH or SMOOTH3 functions however.
by tomfid
Tue Sep 15, 2020 5:24 pm
Forum: Vensim
Topic: Getting the y-axis value
Replies: 13
Views: 262

Re: Getting the y-axis value

You could use something like
sampled marginal cost = SAMPLE IF TRUE( Time<=desired time, marginal cost, marginal cost )
desired time = 9.17
At or after time 9.17, this will show the marginal cost at time 9.17.

However, I'm still not clear on how this is being used, so this may not be useful.
by tomfid
Mon Sep 14, 2020 3:47 pm
Forum: Vensim
Topic: Table only show results for a few years
Replies: 1
Views: 54

Re: Table only show results for a few years

You can bring up the Control Panel, Time Axis tab, and try the "Reset to Full Range" button.
by tomfid
Thu Sep 03, 2020 6:21 pm
Forum: Ventity
Topic: Object reference not set to an instance of an object runtime error
Replies: 6
Views: 159

Re: Object reference not set to an instance of an object runtime error

Can you share the model with us? (Email to info at ventity dot biz or post here, if possible.)
by tomfid
Wed Sep 02, 2020 10:09 pm
Forum: Ventity
Topic: Object reference not set to an instance of an object runtime error
Replies: 6
Views: 159

Re: Object reference not set to an instance of an object runtime error

Does this happen at runtime? Are you running the latest 4.0 beta, or v3?
by tomfid
Tue Sep 01, 2020 8:15 pm
Forum: Ventity
Topic: Lookup Problem w/4.0
Replies: 3
Views: 85

Re: Lookup Problem w/4.0

Thanks.
by tomfid
Tue Sep 01, 2020 6:09 pm
Forum: Ventity
Topic: Lookup Problem w/4.0
Replies: 3
Views: 85

Re: Lookup Problem w/4.0

Seems to work fine for me. What's the symptom?
by tomfid
Tue Sep 01, 2020 3:16 pm
Forum: Vensim
Topic: Getting the y-axis value
Replies: 13
Views: 262

Re: Getting the y-axis value

Ok ... I think I understand what the cost curve is doing. But why go to all the trouble of constructing the curve, when you can simply observe the marginal cost at time 9.17 directly?
by tomfid
Tue Sep 01, 2020 3:00 pm
Forum: Vensim
Topic: INPUT OUTPUT OBJECT
Replies: 2
Views: 98

Re: INPUT OUTPUT OBJECT

Right. I generally use a custom graph only where variables are closely related an have the same units. For example, the inflow and outflow of water from a lake would be good candidates. Otherwise, it's better to create multiple graphs on the screen. It's hard for people to interpret things with diff...
by tomfid
Tue Sep 01, 2020 2:58 pm
Forum: Vensim
Topic: solving difference equation
Replies: 7
Views: 171

Re: solving difference equation

Where you have:

DELAY FIXED( Nban Age1, 1,2.08965e+07 )

you can use

DELAY FIXED( Nban Age1, 1, any_expression )

The only exception is that you can't initialize something to itself, or with other variables in a way that creates a simultaneous equation loop.
by tomfid
Tue Sep 01, 2020 2:54 pm
Forum: Vensim
Topic: Calibration vensim model
Replies: 9
Views: 303

Re: Calibration vensim model

Generally, a parameter is a candidate if it's (a) influential enough to affect the outcome, (b) not redundant with another parameter, and (c) substantially uncertain (not true by definition, like pi, or well known, like the speed of light).
by tomfid
Fri Aug 28, 2020 6:16 pm
Forum: Vensim
Topic: Getting the y-axis value
Replies: 13
Views: 262

Re: Getting the y-axis value

Don't worry, we'll get there.

I'm still not sure what T and components 1..4 represent though.
by tomfid
Fri Aug 28, 2020 5:03 pm
Forum: Vensim
Topic: Getting the y-axis value
Replies: 13
Views: 262

Re: Getting the y-axis value

I don't think I understand what this is trying to do. Is T time, or a time segment, like base/mid/peak? Or is it the time at which a given capacity level is reached? Either way, the condition in your SAMPLE equation is dimensionally inconsistent - you have Marginal Cost Curve=T1, but T1 is in years ...
by tomfid
Fri Aug 28, 2020 3:16 pm
Forum: Vensim
Topic: solving difference equation
Replies: 7
Views: 171

Re: solving difference equation

If you really want your model to use discrete time notation, you can use TIME STEP = 1 with Euler integration, and use the DELAY FIXED function or simply a stock. You would then write something like: y = a*x previous ~ people x previous = DELAY FIXED( x, one day, x0 ) ~ people one day == 1 ~ day TIM...
by tomfid
Fri Aug 28, 2020 3:32 am
Forum: Vensim
Topic: solving difference equation
Replies: 7
Views: 171

Re: solving difference equation

Presumably in your equation x=population, a represents the survival fraction from one year to the next, and b is the inflow of births. In that case, you should rewrite this with stocks and flows, such that: population = INTEG(births-deaths, init pop) births = birth rate*population deaths = death rat...
by tomfid
Wed Aug 26, 2020 4:26 pm
Forum: Vensim
Topic: different output issues
Replies: 3
Views: 127

Re: different output issues

This is possible, especially if the scale of the numbers differs a lot. It's unlikely to matter in any real-world situation. It would be helpful to see your example though.
by tomfid
Wed Aug 26, 2020 3:05 pm
Forum: Vensim
Topic: different output issues
Replies: 3
Views: 127

Re: different output issues

They shouldn't be different. Can you post the .mdl?
by tomfid
Tue Aug 25, 2020 7:41 pm
Forum: Vensim
Topic: Importing Anylogic 7 Model to Vensim
Replies: 2
Views: 99

Re: Importing Anylogic 7 Model to Vensim

I've never seen the raw code for an Anylogic model, but if there's a text version, it might be possible without much effort. If it's not text, or not pure SD, it might be hard - probably easier to replicate by hand, possibly in Ventity if there are agent features in use.
by tomfid
Tue Aug 25, 2020 5:04 pm
Forum: Vensim
Topic: Vensim hangs when switching to Text view
Replies: 8
Views: 184

Re: Vensim hangs when switching to Text view

This is now fixed and will be available in the next release (sooner if you need it - email us with your license details).
by tomfid
Tue Aug 25, 2020 4:11 pm
Forum: Vensim
Topic: Sort Order (for multivariable)
Replies: 21
Views: 439

Re: Sort Order (for multivariable)

The documentation for the allocation process is here: https://www.vensim.com/documentation/allocation_overview.htm The basic idea is that the unit costs are used to construct an aggregate supply curve. Then it computes the market-clearing costs, where demand intersects that curve. Any plant below th...