Search found 2724 matches

by tomfid
Tue Sep 03, 2019 2:16 pm
Forum: Vensim
Topic: Vensim 8 External functions documents & help
Replies: 8
Views: 191

Re: Vensim 8 External functions documents & help

I think it's a terminology gap. If Microsoft uses "workload" to mean which language package is active in Viz Studio, then yes, C++ is what you want.
by tomfid
Tue Sep 03, 2019 2:15 pm
Forum: Vensim
Topic: connecting vensim and online data
Replies: 2
Views: 82

Re: connecting vensim and online data

Depends what you mean by "connect." There are multiple ways to use data in Vensim, and many online climate sources. If you want to scrape data off the web, you'll probably have to write some custom code, but you'd have to tell us more about your use case for advice about how to get it into Vensim. I...
by tomfid
Tue Sep 03, 2019 2:13 pm
Forum: Vensim
Topic: Reference for Vensim's automatic calibration
Replies: 4
Views: 128

Re: Reference for Vensim's automatic calibration

Which algorithm are you using? Powell or MCMC?
by tomfid
Tue Sep 03, 2019 2:12 pm
Forum: Vensim
Topic: Graph export at high resolution (>=300 dpi)
Replies: 3
Views: 101

Re: Graph export at high resolution (>=300 dpi)

Pasting into Paint may be your problem. That throws away the vector graphic and gives you some kind of bitmap. Paste into Word, Powerpoint, or a vector drawing program.
by tomfid
Fri Aug 30, 2019 9:49 pm
Forum: Ventity
Topic: Initializing Entities from a stack?
Replies: 6
Views: 202

Re: Initializing Entities from a stack?

Here are a couple variations. In the "PL1" version, I made the process list approach a little fancier.

In the "2" version, I switched to a linked list.
projectStack.zip
(31.95 KiB) Downloaded 13 times
by tomfid
Fri Aug 30, 2019 10:22 am
Forum: Ventity
Topic: Initializing Entities from a stack?
Replies: 6
Views: 202

Re: Initializing Entities from a stack?

I'll take a look. I'm not sure about "more elegant" but you could avoid the process list by making the stack into a linked list by adding a "next in stack" attribute to each stack item. On the other hand, the process list is nice because you could change the priority for selecting the next item dyna...
by tomfid
Fri Aug 30, 2019 10:05 am
Forum: Vensim
Topic: Structure and vensim equations for the macro "DELAY FIXED"
Replies: 2
Views: 74

Re: Structure and vensim equations for the macro "DELAY FIXED"

It's an infinite order delay, which means that effectively it's an aging chain where the number of stocks is equal to delay_duration/TIME_STEP, and each stock has time constant = TIME_STEP.
by tomfid
Thu Aug 29, 2019 1:41 am
Forum: Vensim
Topic: Use of time zone in Vensim
Replies: 4
Views: 92

Re: Use of time zone in Vensim

Seems like more of a discrete event simulation problem.

You could assign each team member an integer time zone number, and search for viable times that are within a certain window overlap from the zone number, modulo 24.

It's hard to say more without knowing more about the problem statement.
by tomfid
Wed Aug 28, 2019 5:53 pm
Forum: Ventity
Topic: summing over data entity types
Replies: 1
Views: 77

Re: summing over data entity types

Possibly - we'll check it out.

As a workaround, you could move the numbers over to a regular entity and aggregate there.
by tomfid
Wed Aug 28, 2019 3:15 am
Forum: Vensim
Topic: Use of time zone in Vensim
Replies: 4
Views: 92

Re: Use of time zone in Vensim

What do you want to do with the time zone? How about using an integer from 1 to 24?
by tomfid
Mon Aug 26, 2019 2:42 pm
Forum: Vensim
Topic: data science
Replies: 2
Views: 85

Re: data science

There are many that implement large portions of this. Here's one example:
https://scholar.harvard.edu/jalali/publ ... e-petition
There's a version in the SD conference proceedings that includes the model.
by tomfid
Mon Aug 26, 2019 2:22 pm
Forum: Ventity
Topic: changing the "Map Layer"
Replies: 3
Views: 111

Re: changing the "Map Layer"

You can use the tooltip field. Not sure what the status is, but here's the latest from the dev team: The current tooltip implementation goes as follows : 1) You can put any text you want 2) some html formatting applies, like <br> for new line and <b></b> for bold 3) variables are introduced using cu...
by tomfid
Mon Aug 26, 2019 2:18 pm
Forum: Vensim
Topic: Using more than two Subscripts
Replies: 6
Views: 116

Re: Using more than two Subscripts

If most of your values are 0, you can put 0 in the equation,
const[x,y,z] = 0

Then use a .cin file to override the few nonzero values:
const[b,y2,z1] = 3.141
by tomfid
Mon Aug 26, 2019 2:15 pm
Forum: Vensim
Topic: Using more than two Subscripts
Replies: 6
Views: 116

Re: Using more than two Subscripts

In both of your screenshots, you have 2 dimensions, but only 1 row of data. That will never work. If you have 1 dimension: 0, 0, 0 2 dimensions: 0, 0, 0; 1, 1, 1; For 3 or more dimensions, you can use element-by-element definitions. For example, if you have: X : a, b Y : y1,y2 Z : z1,z2 you can defi...
by tomfid
Mon Aug 26, 2019 3:59 am
Forum: Ventity
Topic: changing the "Map Layer"
Replies: 3
Views: 111

Re: changing the "Map Layer"

It's a basemap - it'll show resolution-appropriate material scaled to the rest of your data. But if you use it too much, it'll probably get shut down by the host. It's a loose end we're working on.

You can disable it via the Layer menu.
by tomfid
Mon Aug 26, 2019 3:57 am
Forum: Ventity
Topic: Initializing Entities from a stack?
Replies: 6
Views: 202

Re: Initializing Entities from a stack?

There is a way to do this, but it's a little indirect. Create an entitytype A containing just the initialization data, then a paired entitytype B with the dynamics. Then the A entities serve as the stack, and you can use the next available A to create a B via an action. This is a little wasteful, be...
by tomfid
Thu Aug 22, 2019 7:28 pm
Forum: Ventity
Topic: Many-to-Many Relationship Cohorts
Replies: 8
Views: 191

Re: Many-to-Many Relationship Cohorts

For completeness, here's another version, implemented the other way:
- Market is not a singleton
- Fleet has a compound key (market|size|type)
VehicleCohorts7.zip
(20.79 KiB) Downloaded 14 times
by tomfid
Thu Aug 22, 2019 4:16 pm
Forum: Vensim
Topic: Working with Levels in Vensim
Replies: 2
Views: 83

Re: Working with Levels in Vensim

Another possibility is to create a reporting variable that reflects the stock+current flow.
by tomfid
Thu Aug 22, 2019 3:53 pm
Forum: Vensim
Topic: CRASH: Vensim 8 macOS; while modifying graphs
Replies: 1
Views: 72

Re: CRASH: Vensim 8 macOS; while modifying graphs

This appears to be in the wxwidgets lib. I'm logging tickets for all these - keep the comments coming.
by tomfid
Thu Aug 22, 2019 3:52 pm
Forum: Vensim
Topic: A simple experiment - gone wrong.
Replies: 1
Views: 64

Re: A simple experiment - gone wrong.

What you need is a discrete event that intermittently drains/replaces the part. This might be helpful: https://vensim.com/discrete-stochastic/
by tomfid
Thu Aug 22, 2019 3:49 pm
Forum: Vensim
Topic: Unit : It is possible to have (k*pas) *(k*km) = M*km*pas
Replies: 2
Views: 73

Re: Unit : It is possible to have (k*pas) *(k*km) = M*km*pas

You could define a variable called "kilos per mega" with units k*k/M and use that to make the conversion.
by tomfid
Thu Aug 22, 2019 2:23 pm
Forum: Ventity
Topic: Many-to-Many Relationship Cohorts
Replies: 8
Views: 191

Re: Many-to-Many Relationship Cohorts

1. I could have left the FleetID alone, in which case the Cohort could look up Size and Type via a reference to the Fleet to which it belongs. Either way, the Cohort needs to have attributes storing the key for the Fleet. 2. True - this is often the case. 3. You always need a reference to access inf...
by tomfid
Wed Aug 21, 2019 10:53 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 24
Views: 1390

Re: Integrating time step of optimization problem

In the model above, you may discover that [s3] can sustain a fairly large positive bias. I think that's because there's a big jump in marginal cost to the next-cheapest producer [s6]. So, s3 could bid just below s6's marginal cost, rather than at its own marginal cost. That wouldn't hold up in a mar...
by tomfid
Wed Aug 21, 2019 10:37 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 24
Views: 1390

Re: Integrating time step of optimization problem

Here's a simpler model, in which everyone bids marginal cost and receives the clearing price. DEMAND AT PRICE elec 0.mdl If you play with the bias parameter, you can see that it's not really possible for one supplier to improve its outcome more than a tiny bit by bidding strategically. So, as you'd ...
by tomfid
Wed Aug 21, 2019 10:02 pm
Forum: Vensim
Topic: Integrating time step of optimization problem
Replies: 24
Views: 1390

Re: Integrating time step of optimization problem

I've attached two models, neither of which is really right, but both in the ballpark. DEMAND AT PRICE elec 2.mdl DEMAND AT PRICE elec 1.mdl #1 implements what I originally suggested, which is that everyone bids close to MAX( marg cost, expected price ). That actually implements collusion, and the pr...