Ventana software support forum

Whole model outside the crop is a weird behavior I haven't seen. If you have a simple example ...

k : k1-k10
y[k] = x[k]
y active[k] = IF THEN ELSE( k=3, 1, 0)
y out = SUM( y[k!]*y active[k!] )

Another option for picking a single value would be,

y out = VECTOR ELM MAP( y[k1], offset )

where offset is the index of the value you want as a 0-based offset from k1.

You can use VECTOR SELECT or SUM for this, combined with an indicator variable that shows which of the RHS elements to select.

This turned out to be some pretty tricky subscripting, but I haven't thought of a nicer way to do it.

This submodel may do what is required. There are two arbitrary input vectors that are sampled at at 10hr intervals, starting at time 10. The expected product[hN] is therefore approximately N plus some small random noise. There are a couple unit errors in the inputs from my abuse of the PINK NOISE fu...

I think it's possible to attach the debugger to the xfn dll when the model runs, but I don't remember the details. Then you could peek inside to observe execution.

A variant on representing the vector as a stock is using SAMPLE IF TRUE.

Model>Settings>Information will give you the equation count, which is the best indication of effective size.

Re 4: there are some new I/O controls for subscript selection on screen, or people can use the Subscript Control. However, there isn't a way to do aggregation (SUM etc.) on the fly - you have to create the variables in advance.

It's more parsimonious to load different data files at runtime, but you can also do something like the following:

scenario : low, mid, hi

data pop[scenario]

data pop selected = IF THEN ELSE(active scenario = low, data pop[low] ... etc.

Whether parsimonious matters is just a function of runtime.

There shouldn't really be any prereqs for PLE (other than fairly minimal machine and OS requirements). Do you get the option to submit a crash report when it crashes? Are you using the latest version 10.x?

In development:

I've ticketed this for improvement.

I may be dense, but I'm still not getting it. If you can pass two vectors into a function to muliply x[k]*z[k inverted] you can do the same with VECTOR ELM MAP. I can create an example if helpful.

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)).