Search found 2992 matches

by tomfid
Sat Aug 08, 2020 9:16 pm
Forum: Ventity
Topic: Running Ventity on a Mac using a Windows emulator
Replies: 1
Views: 11

Re: Running Ventity on a Mac using a Windows emulator

What OS version is your emulator running? 7, 8 or 10?
by tomfid
Fri Aug 07, 2020 4:34 pm
Forum: Vensim
Topic: The question aboujt time step and units for Time
Replies: 1
Views: 27

Re: The question aboujt time step and units for Time

Are you using an older version? Some of the output tools may crash with long time series, but not in the latest. I would recommend running the model with a time step of 1 hour, then aggregating profits up to a year by taking a moving average. You can create a time base for years, or use the calendar...
by tomfid
Tue Aug 04, 2020 3:42 pm
Forum: Vensim
Topic: MS C/C++ DLLs for Vensim DSS models
Replies: 6
Views: 85

Re: MS C/C++ DLLs for Vensim DSS models

Unfortunately, now that Apple and MS have adopted a steady drumbeat of forced updates and reduced backward compatibility, somewhat more frequent updates may be needed, because we have to follow the operating system's lead.
by tomfid
Mon Aug 03, 2020 1:21 pm
Forum: Vensim
Topic: MS C/C++ DLLs for Vensim DSS models
Replies: 6
Views: 85

Re: MS C/C++ DLLs for Vensim DSS models

That would be a matter of setting the path in Tools>Options>Startup.
by tomfid
Sun Aug 02, 2020 8:48 pm
Forum: Vensim
Topic: MS C/C++ DLLs for Vensim DSS models
Replies: 6
Views: 85

Re: MS C/C++ DLLs for Vensim DSS models

The issue here is that v8+ changed the external function library headers somewhat, so things need to be recompiled. You can still use C, and most simple code won't need to change.
by tomfid
Sun Aug 02, 2020 2:43 am
Forum: Vensim
Topic: Creating an "evolving" subscript or subrange?
Replies: 1
Views: 30

Re: Creating an "evolving" subscript or subrange?

You may be able to do what you need with VECTOR SELECT or VECTOR ELM MAP. For really dynamic lists, you need Ventity instead.
by tomfid
Wed Jul 29, 2020 9:17 pm
Forum: Vensim
Topic: Passing a cost at a discrete time to a variable
Replies: 13
Views: 1651

Re: Passing a cost at a discrete time to a variable

In the example model, which is actually at https://www.vensim.com/documentation/fn_allocate_by_priority.htm , the language for "supply" and "demand" needs to be changed, because "supply" in your context is total electricity demand, "demand" is generation capacity by [plant], and "shipments" is actua...
by tomfid
Tue Jul 28, 2020 3:30 pm
Forum: Vensim
Topic: bad lookup initializing delay
Replies: 18
Views: 716

Re: bad lookup initializing delay

Makes sense. Because the number of units is small, it might be simpler to have an array of individual units, rather than using conveyors. Then each unit can easily have a unique retirement date, and that date can be changed if there's a retrofit, accident, etc.
by tomfid
Tue Jul 28, 2020 3:19 pm
Forum: Vensim
Topic: continue during year
Replies: 6
Views: 78

Re: continue during year

OK ... it sounds like you want a repeating step that is 0 at the start of the year, switches to 1 at some point during the year, then resets to 0 and starts over. Something like this:
day2year.mdl
(3.67 KiB) Downloaded 4 times
by tomfid
Tue Jul 28, 2020 2:45 pm
Forum: Vensim
Topic: problem with my graph
Replies: 3
Views: 113

Re: problem with my graph

The wastewater collected variable seems OK, it's just the "water in dam" concept that seems to have no physical meaning.

I would expect something like:

wastewater collected = water supply * fraction water collected
by tomfid
Tue Jul 28, 2020 2:40 pm
Forum: Vensim
Topic: Passing a cost at a discrete time to a variable
Replies: 13
Views: 1651

Re: Passing a cost at a discrete time to a variable

I would try something like the following: - grab the ALLOCATE AVAILABLE.mdl sample in the help system https://www.vensim.com/documentation/ - rename/reinterpret "total supply" as "electricity demand" - replace the "region" subscript with your plant type subscript, e.g., the hierarchical version plan...
by tomfid
Tue Jul 28, 2020 2:25 pm
Forum: Vensim
Topic: File copies
Replies: 3
Views: 29

Re: File copies

Tools>Settings>Startup lets you set a backup file path to keep these out of your directory, though I generally don't.
by tomfid
Tue Jul 28, 2020 2:15 pm
Forum: Vensim
Topic: bad lookup initializing delay
Replies: 18
Views: 716

Re: bad lookup initializing delay

I generally avoid conveyors, because the discrete lifetime implied is not realistic for most capital goods. Early or delayed retirement is common. A third order delay is often sufficient to capture the distribution. A conveyor is more realistic for something like mortgages or bonds, which have a fix...
by tomfid
Mon Jul 27, 2020 3:45 pm
Forum: Vensim
Topic: continue during year
Replies: 6
Views: 78

Re: continue during year

Not sure I understand the question. Should the parameter represent the day of the year, and therefore have a range (1,365), or should it be the day from day 0, with range 1 ... n years*365? Should the output be one value, or three values (one for each subscript element)? Should the output be a step ...
by tomfid
Mon Jul 27, 2020 3:58 am
Forum: Vensim
Topic: subscript combine
Replies: 7
Views: 200

Re: subscript combine

I forgot one thing - you need to map sub1 to the k ranges:

sub1 : (n1-n3) -> klower,kupper
by tomfid
Fri Jul 24, 2020 1:44 am
Forum: Vensim
Topic: subscript combine
Replies: 7
Views: 200

Re: subscript combine

Create Klower, Kupper first, then create subK.
by tomfid
Thu Jul 23, 2020 7:53 pm
Forum: Vensim
Topic: subscript combine
Replies: 7
Views: 200

Re: subscript combine

There are probably several ways to accomplish this. Not knowing anything about the meaning of the variables, it's hard to suggest the best option. One would be: sub1 : (n1-n3) subK : kLower, kUpper kLower : (k1-k3) kUpper : (k4-k6) Then you can write: newvec[kLower] = array1[sub1] newvec[kUpper] = a...
by tomfid
Wed Jul 22, 2020 3:31 pm
Forum: Vensim
Topic: problem with my graph
Replies: 3
Views: 113

Re: problem with my graph

I find some variances between your variables and your units. For example, I would expect "wastewater collected" to be a physical measure in liters/month, but it's dmnl. What does that mean? Similarly, "water stored in dam" seems like an arbitrary transformation with unphysical units. It seems like "...
by tomfid
Tue Jul 21, 2020 5:15 pm
Forum: Vensim
Topic: Conditional reliability on SD
Replies: 2
Views: 212

Re: Conditional reliability on SD

I think what this implies is that products in each state need some disaggregation, either with a coflow of some attribute ("extent worn out") or additional states indicating number of uses (things used once, used twice, ...).
by tomfid
Tue Jul 21, 2020 2:15 pm
Forum: Vensim
Topic: Passing a cost at a discrete time to a variable
Replies: 13
Views: 1651

Re: Passing a cost at a discrete time to a variable

I can, but it'll probably be a few days because the SD conference is underway. Hopefully someone else can jump in first.
by tomfid
Sat Jul 18, 2020 4:07 pm
Forum: Vensim
Topic: Passing a cost at a discrete time to a variable
Replies: 13
Views: 1651

Re: Passing a cost at a discrete time to a variable

What is the purpose of this change? Is it so that you can have synthetic plants that are dispatched separately? If so, you could build up your array of plants hierarchically, as: hydro : (h1-h10) coal : (c1-c10) etc. plant : hydro, coal, oil, gas Then new hydro capacity for each of the 10 hydro subr...
by tomfid
Fri Jul 17, 2020 3:34 pm
Forum: Vensim
Topic: Error (Simultaneous Equation Involving...)
Replies: 8
Views: 219

Re: Error (Simultaneous Equation Involving...)

Similarly, on your second page, you're using boxes for visual emphasis. This is fine, but it limits your ability to communicate with anyone who's expecting the System Dynamics convention, boxes = stocks.
by tomfid
Fri Jul 17, 2020 1:31 am
Forum: Vensim
Topic: Error (Simultaneous Equation Involving...)
Replies: 8
Views: 219

Re: Error (Simultaneous Equation Involving...)

If demand = a*pop + b*GDP, then it should be an auxiliary (no box, no inflow).
by tomfid
Thu Jul 16, 2020 7:24 pm
Forum: Vensim
Topic: Error (Simultaneous Equation Involving...)
Replies: 8
Views: 219

Re: Error (Simultaneous Equation Involving...)

Similarly, your demand should not be diagrammed as a stock-flow system (the equations might be OK).
by tomfid
Tue Jul 14, 2020 2:23 pm
Forum: Vensim
Topic: Keep a subscript element name attached to its value after a VECTOR REORDER?
Replies: 9
Views: 193

Re: Keep a subscript element name attached to its value after a VECTOR REORDER?

There's no way to sort the subscript element names themselves. For computational purposes, you can access everything you need numerically (I assume you've seen the sample models). Do you need something special for display purposes?