Search found 2508 matches

by tomfid
Thu Apr 18, 2019 6:16 pm
Forum: Vensim
Topic: Questions about random Weibull
Replies: 14
Views: 1000

Re: Questions about random Weibull

Here are three different parameterizations, using terminology from NIST, Wikipedia and Wolfram Mathworld:
RANDOM functions.mdl
(38.93 KiB) Downloaded 1 time
by tomfid
Wed Apr 17, 2019 9:26 pm
Forum: Vensim
Topic: Questions about random Weibull
Replies: 14
Views: 1000

Re: Questions about random Weibull

Try the sample model attached to the help system topic for the random functions. It's in c:\users\public\vensim if your OS won't let the help link work.
by tomfid
Wed Apr 17, 2019 8:03 pm
Forum: Vensim
Topic: Questions about random Weibull
Replies: 14
Views: 1000

Re: Questions about random Weibull

Terminology for the Weibull distribution is not well standardized, and most sources don't use alpha and beta. Can you give us a reference you're trying to match?
by tomfid
Wed Apr 17, 2019 12:57 pm
Forum: Vensim
Topic: Running multiple models
Replies: 3
Views: 11

Re: Running multiple models

It sounds like you're running a chain of models, where the output from one is the input to the next. This is easy with a command script (requires Vensim DSS).
by tomfid
Mon Apr 15, 2019 1:49 pm
Forum: Vensim
Topic: Hearne' method
Replies: 2
Views: 14

Re: Hearne' method

I assume you mean this? https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1939-7445.2009.00058.x The paper is paywalled, but I'm going to speculate that in general it would be tricky to implement. You'd have to have a library of functions with desired properties that meet all the reality checks need...
by tomfid
Mon Apr 08, 2019 9:19 pm
Forum: Vensim
Topic: Read in time-dependent array from Excel
Replies: 1
Views: 35

Re: Read in time-dependent array from Excel

If you're using GET XLS, it can only handle one dimension (plus time) at a time. So, you'd need three equations to import this: data[USA,importCountries] = GET XLS DATA( ... , 'C5' ) data[Germany,importCountries] = GET XLS DATA( ... , 'C8' ) data[China,importCountries] = GET XLS DATA( ... , 'C11' ) ...
by tomfid
Mon Apr 08, 2019 9:05 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

Great - hopefully things can move forward now.
by tomfid
Mon Apr 08, 2019 8:09 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

Global_model-mod+biogeochem.mdl
(602.96 KiB) Downloaded 2 times
This is a working merger (it parses and runs, but crashes with an fp error pretty quickly). I had to modify the equations differently - modifying the host global model's j and k ranges rather than the biogeochem model.
by tomfid
Mon Apr 08, 2019 6:52 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

Was the modified BIOGEOCHEM model runnable before you attempted the paste? It appears that it uses a lot of individual subscript elements in the equations, so it would be nontrivial to rename the elements.
by tomfid
Mon Apr 08, 2019 5:02 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

I think part of the problem may be that you have j and k ranges in both models, presumably with different ranges and interpretations. Since the biogeochem model is simpler, I'd rename all the ranges, subranges and elements there before doing the copy/paste. In any case, i, j, k etc. would usually be...
by tomfid
Mon Apr 08, 2019 4:51 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

When you paste across models, Vensim generally tries to bring the needed subscript families along. However, if there are overlapping names of elements, ranges or subranges, this may cause a conflict. I think that might be what's happened here. When I look at the subscript control in my copy (in 7.3....
by tomfid
Mon Apr 08, 2019 4:06 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

I can open the model using File>Edit File to bring it into the text editor. There seem to be a lot of subscript errors: ERROR: Unspecified subscript equation for - j10. ERROR: Unspecified subscript equation for - j11. ERROR: Unspecified subscript equation for - j12. ERROR: Unspecified subscript equa...
by tomfid
Mon Apr 08, 2019 4:03 pm
Forum: Vensim
Topic: Varformat error 1071225242
Replies: 12
Views: 70

Re: Varformat error 1071225242

Do you have an earlier, working version we can compare?
by tomfid
Thu Apr 04, 2019 9:06 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 10
Views: 107

Re: sensitivity analysis (vensim)

Try the samples in the help system: http://vensim.com/documentation/usr15.htm
by tomfid
Thu Apr 04, 2019 9:05 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 10
Views: 107

Re: sensitivity analysis (vensim)

What is shown on this plot? If it's a parameter, it will be constant.
by tomfid
Thu Apr 04, 2019 7:51 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 10
Views: 107

Re: sensitivity analysis (vensim)

Right-click the sensitivity graph tool and change the options to show confidence bounds rather than individual traces.

From your second graph, it looks like the range of behavior is very narrow.
by tomfid
Thu Apr 04, 2019 12:57 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 10
Views: 107

Re: sensitivity analysis (vensim)

Or just Tools>Analysis>New to reload a new copy of the toolset.
by tomfid
Thu Apr 04, 2019 3:30 am
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 10
Views: 107

Re: sensitivity analysis (vensim)

Try loading a new Analysis Toolset?
by tomfid
Thu Apr 04, 2019 12:41 am
Forum: Ventity
Topic: Ventity Optimization dialog a bit wonky?
Replies: 3
Views: 81

Re: Ventity Optimization dialog a bit wonky?

I've put in a ticket for this.
by tomfid
Wed Apr 03, 2019 1:09 pm
Forum: Vensim
Topic: Please, help
Replies: 2
Views: 57

Re: Please, help

Also, as a general practice, you should not bury numbers that have dimensions in your equations. Each item (1045, 180) should be made a separate named variable with units.
by tomfid
Tue Apr 02, 2019 11:17 pm
Forum: Vensim
Topic: Crashes frequently on Windows 10
Replies: 11
Views: 118

Re: Crashes frequently on Windows 10

Strange. I can paste with a prefix all day long, no issues.
by tomfid
Tue Apr 02, 2019 10:07 pm
Forum: Vensim
Topic: Please, help
Replies: 1
Views: 52

Re: Please, help

Presumably you have a stock of water in the reservoir, with an inflow (river flow or rainfall or something, presumably exogenous) and an outflow (discharge). I would guess that there's a mechanism something like the following: water in reservoir = INTEG( inflow - discharge, initial water ) inflow = ...
by tomfid
Mon Apr 01, 2019 6:15 pm
Forum: Vensim
Topic: Crashes frequently on Windows 10
Replies: 11
Views: 118

Re: Crashes frequently on Windows 10

Converter = Auxiliary
by tomfid
Mon Mar 25, 2019 5:02 pm
Forum: Vensim
Topic: Giving Excel Data
Replies: 7
Views: 152

Re: Giving Excel Data

Two options: 1. Run the model in days, using the same numbering as Excel dates. (An Excel date is really a number like 34582.) 2. In Excel, create a time row/column that translates dates to a decimal year, week, etc. For example, if cell A2 contains a date, you could translate that to a decimal year...