Search found 2465 matches

by tomfid
Mon Mar 18, 2019 6:36 pm
Forum: Vensim
Topic: How to put excel database in variables?
Replies: 5
Views: 16

Re: How to put excel database in variables?

You can do that. There are some drawbacks - for example, you can't distinguish the interpolated values from real data points - but it works.
by tomfid
Fri Mar 15, 2019 4:16 am
Forum: Vensim
Topic: Crash Upon Adding New Variable, Possible Memory Issue
Replies: 8
Views: 38

Re: Crash Upon Adding New Variable, Possible Memory Issue

I can replicate the crash (no explanation yet).
by tomfid
Thu Mar 14, 2019 7:34 pm
Forum: Vensim
Topic: Giving Excel Data
Replies: 4
Views: 24

Re: Giving Excel Data

The model time is in Model>Settings>Time Bounds

The data time horizon will be in your spreadsheet. Model and data time units have to match. Excel dates generally won't work, because internally they are a number representing the days elapsed since Jan 1 1900.
by tomfid
Thu Mar 14, 2019 7:05 pm
Forum: Vensim
Topic: Giving Excel Data
Replies: 4
Views: 24

Re: Giving Excel Data

This means that the time over which your data is available does not correspond to the time axis of the model. You will get that warning if, for example, your model starts in 1990 but your oil price data starts in 2010.
by tomfid
Wed Mar 13, 2019 3:10 pm
Forum: Vensim
Topic: model protection
Replies: 1
Views: 20

Re: model protection

You can distributed models in published form (vpm) with password protection to prevent re-saving. It's not uncrackable, but certainly makes copying inconvenient. You should mark the top view of your model with a conspicuous notice of copyright and license, and use the Model>Settings>Info field to pr...
by tomfid
Wed Mar 13, 2019 1:22 pm
Forum: Vensim
Topic: vensim and qgis
Replies: 5
Views: 61

Re: vensim and qgis

VentityGIS.png
VentityGIS.png (1.31 MiB) Viewed 7 times
by tomfid
Wed Mar 13, 2019 1:20 pm
Forum: Vensim
Topic: vensim and qgis
Replies: 5
Views: 61

Re: vensim and qgis

You can already do it via data import/export, as in Vensim, but soon Ventity will have native map display capability.
by tomfid
Mon Mar 11, 2019 4:43 pm
Forum: Vensim
Topic: SIMULATE>SETVAL does not change variable value when running vensim with command file?!
Replies: 10
Views: 41

Re: SIMULATE>SETVAL does not change variable value when running vensim with command file?!

If you really want to ensure separation, you can set the model value to :NA: - that way the model will generate errors or na values if the .cin file does not populate the constant.

I usually have a usable default value in the equation, and use .cin files for experiments or scenarios.
by tomfid
Mon Mar 11, 2019 4:39 pm
Forum: Vensim
Topic: Not able to attach additional files while editing a post
Replies: 6
Views: 26

Re: Not able to attach additional files while editing a post

... or include it in a zip archive.
by tomfid
Fri Mar 01, 2019 5:34 pm
Forum: Vensim
Topic: Unable to converge simultaneous Equations at Time Error
Replies: 8
Views: 79

Re: Unable to converge simultaneous Equations at Time Error

I forgot to mention one other item: I think "profit spent on irrigation" and "irrigation cost" might be conceptually the same thing?
by tomfid
Fri Mar 01, 2019 5:27 pm
Forum: Vensim
Topic: Unable to open VDF when it's not locked
Replies: 1
Views: 32

Re: Unable to open VDF when it's not locked

I think the problem is that the vdf has not been created, due to the previous error:
STOP: Problems encountered in the simulation.

Not sure what causes that - perhaps a missing input file. You might try turning off NOINTERACTION to see if you get any additional queries.
by tomfid
Fri Mar 01, 2019 5:23 pm
Forum: Vensim
Topic: Unable to converge simultaneous Equations at Time Error
Replies: 8
Views: 79

Re: Unable to converge simultaneous Equations at Time Error

I think you want something more like this:
01032019 v2.mdl
(13.93 KiB) Downloaded 5 times
by tomfid
Fri Mar 01, 2019 5:17 pm
Forum: Vensim
Topic: Unable to converge simultaneous Equations at Time Error
Replies: 8
Views: 79

Re: Unable to converge simultaneous Equations at Time Error

Actually, I guess you have implicit units conversions in the integration equations. This may be technically OK but is usually confusing for users. Probably better to have 2 or 3 distinct stock-flow structures: one for water, one for crops and one for money. As it is now defined, net income appears t...
by tomfid
Fri Mar 01, 2019 5:13 pm
Forum: Vensim
Topic: Unable to converge simultaneous Equations at Time Error
Replies: 8
Views: 79

Re: Unable to converge simultaneous Equations at Time Error

I think the simultaneity here signals a conceptual issue, which would be revealed if you completed the definition and checking of units. The basic problem is that net farm income is presumably denominated in money, and therefore can't possibly be connected by flows to the rest of the stock-flow stru...
by tomfid
Fri Mar 01, 2019 3:39 pm
Forum: Vensim
Topic: Simultaneous loop error
Replies: 6
Views: 1510

Re: Simultaneous loop error

Check the sample model referenced above - typically located in C:\Users\Public\Vensim\Models\Sample\EXTRA
by tomfid
Tue Feb 26, 2019 7:49 pm
Forum: Vensim
Topic: Extract a value at a specified time from a stock
Replies: 1
Views: 39

Re: Extract a value at a specified time from a stock

You can't extract the 2015 value from a stock throughout the run, because that would be acausal. SAMPLE IF TRUE works if you want the 2015 value at 2015 or later. You can initialize the SAMPLE to :NA: if you want to be able to detect whether the sampling has happened yet. If you need the future valu...
by tomfid
Mon Feb 25, 2019 2:30 pm
Forum: Vensim
Topic: vensim and qgis
Replies: 5
Views: 61

Re: vensim and qgis

Ventity is also getting some GIS capabilities this year.
by tomfid
Mon Feb 25, 2019 2:30 pm
Forum: Vensim
Topic: vensim and qgis
Replies: 5
Views: 61

Re: vensim and qgis

No, but you can do 2 things:

- Export the attribute table from a shapefile (or similar) and read it in as constants for initializing a Vensim model.
- Export run output (vdf) from Vensim as .csv and display the result in qgis via Layer>Add Layer>Add Delimited Text Layer.
by tomfid
Fri Feb 22, 2019 5:40 pm
Forum: Vensim
Topic: how can I use Vensim to identify all causal loops?
Replies: 3
Views: 69

Re: how can I use Vensim to identify all causal loops?

Note that the loops tool only finds all the loops through a given variable, so you may need to use it in several locations if your model is not strongly connected.
by tomfid
Wed Feb 20, 2019 4:07 pm
Forum: Vensim
Topic: How to change external function
Replies: 7
Views: 131

Re: How to change external function

You'll need the .c source code for the functions you're using.
by tomfid
Wed Feb 20, 2019 2:35 pm
Forum: Vensim
Topic: How to change external function
Replies: 7
Views: 131

Re: How to change external function

Users\public\vensim\cfiles isn't part of the Vensim distribution - could you have received that from whoever wrote the code for the external function?
by tomfid
Fri Feb 15, 2019 3:01 pm
Forum: Vensim
Topic: Question about import dataset into Vensim
Replies: 7
Views: 122

Re: Question about import dataset into Vensim

I think you were importing via Model>Import Dataset...

For .dat format, you want the next menu item, "from .dat format..."
by tomfid
Wed Feb 13, 2019 8:33 pm
Forum: Vensim
Topic: Sens2File Question
Replies: 1
Views: 65

Re: Sens2File Question

There isn't a way to do this with SENS2FILE, but the Stats tool has customizable quantiles. It also gives you the SD directly. Another option would be to use the interquartile range and adjust: IQR = 1.35*SD (see https://math.stackexchange.com/questions/1597937/ratios-of-median-mean-and-standard-dev...