Ventana software support forum

Models are fully portable. With an older version like 7.3, you'll probably see some font/format/scale diferences in the diagram, but nothing that can't be adjusted quickly.

You can fix that by extracting the inner lookup from the outer sum, as in the attached version.

An FEA would increase the computational time beyond reason. I know, I have run the FEAs individually. The point is that an FEA or this equation is only one small component of a much larger system. I need to keep computational time low and within reason to run sensitivity. I do not see that this is ...

If this can be done in Excel, it almost certainly can be done in Vensim arrays, which would be a lot less work than the xfn route.

Is this by any chance heat transfer in a ground loop? Seems like a simple FEA would be a lot easier and more transparent than the "reduced" form above.

The function code might be OK, but it needs to be wrapped in the Vensim external function infrastructure (there's an example in the samples directory tree).

When I see something like this, I immediately think "hidden states". Unless this is something really pathological, there can't really be 262000 meaningful terms in the expression. Presumably there's some underlying system described by this equation that could be described at a more fundame...

This isn't extrapolating because it isn't using LOOKUP EXTRAPOLATE. gfunction lookup from Excel[borehole array size!](time to get) needs to be LOOKUP EXTRAPOLATE( gfunction[size!], time to get )

Even if the code were identical, it might be hard to get them to match - they'd have to be using the same Mersenne prime internally, and the number of draws has to be identical (Vensim makes an extra draw during model initialization). Also, Vensim adds an arbitrary integer offset to the seed. A more...

v10 is a pretty big upgrade from 7. There will be some interface changes that take getting used to, but it's worth it.

Sometimes it's easier to do this kind of thing in the text editor, because you can search for the offending strings and then manually delete the associated variables or elements.

What version are you on? Recent 10.x can handle variable arguments.

You can always write MIN(a,MIN(b,c)).

I assume we're not talking about superposition in the quantum sense. From one point, it's not clear how the terms evolve. For example, How would this be defined at t = ts? Does addition of terms imply that Tf,5 = Ts + blabla + 1/2piks( ... ) * g( (t5-t0)/ts )? Is it recursive, so Tf,n = Tf,n-1 + one...

The API of the multicontext library is basically the same as the regular dll/shared library, so it would probably work. The multicontext library is a separate license though.

If so, admin's solution is correct, albeit a little inefficient because it does the lookup on all 5 response columns. There might be a faster way to do that with VECTOR LOOKUP, but I doubt it's worth the complexity. If you want extrapolation from the endpoints, rather than interpolation within the t...

The 2D vector lookup definitely has 2 dimensions, but I don't think that's what you want. It sounds like you want to interpolate over time (row) with extrapolation, but not over borehole (column), which is categorical rather than continuous?

This is ticketed for improvement.

If you open the svg in an editor like Inkscape and ungroup the drawing, the cropped elements are revealed (at least in some cases I've encountered).

Ah yes ... turns out there is one, the VECTOR LOOKUP.mdl in the examples that install with Vensim (look in users/public/vensim/models). https://vensim.com/documentation/fn_vector_lookup.html?q=vector+lookup The example uses mode 0 (regular lookup, no extrapolation) but if you change the mode switch ...

Good catch BTW. I've copied to my blog (with credit): https://metasd.com/2024/12/case-strict-unit-testing/

This is a very interesting discovery. The equations in question are: maturation 14 to 15 = ( ( Population 0 To 14 ) ) * ( 1 - mortality 0 to 14 ) / 15 Units: Person/year The fractional rate at which people aged 0-14 mature into the next age cohort (MAT1#5). ******************************************...

Also it was Thanksgiving holiday in the US.

If I understand, you want a 2D lookup table, with extrapolation at the edges?

I think you'd have to do it with VECTOR LOOKUP in two steps. I'll check whether I have an example.

Do the shipment paths include movement within ABC, XYZ, or do they pass through a distinct set of cities unrelated to the endpoints (StLouis, Denver, Omaha)?

(I'm just looking for a special case here.)

This is definitely an LP-type problem. I'm not sure the LPSOLVE integration is complete enough to handle this "off the shelf" but it's certainly a possibility.

Apologies for the broken link - now fixed. The infection series also installs with Ventity in the samples folder, so you probably already have a copy.

This is a nontrivial problem. For the commodity case, like electricity where you don't care which electron ends up where, it can be solved with FIND ZERO. However, I'm not sure that's true here.

Are ABC and XYZ the same set of cities, or do the paths include additional nodes?