Ventana software support forum

This sounds like a problem in the macro code rather than vensim_get_val - the function returns floating point numbers, so it's not clear what it would even mean to be missing dots.

Right - so I guess your 'Vensim_PYEAR' points to a range, not a single cell?

I think we'll have to look at the code to see what's going on.

Does your Excel procedure use DDE or the DLL?

It's just an easy way of generating a lot of possible input behaviors from one structure.

The best way to understand it is to run it in synthesim - vary the parameters, and see what happens.

Note this warning in the help for the function: Lastcell can be left blank '' with GET DIRECT SUBSCRIPTS but this will generally not work with GET XLS SUBSCRIPTS. The empty ' ' entry for the last cell argument might be the problem. Thanks for the good documentation - we'll look into this - I've had ...

https://www.vensim.com/documentation/23320.htm

I've tested some code for caching the data, resulting in a significant speedup, which will make it's way into a future release.

The seed is really an ID # for a random stream. Internally, Vensim creates a separate generator for each stream. Each time a function is called, it looks up the appropriate generator by ID and returns the next draw. Two RANDOM functions that use the same ID interact, because they're both consuming d...

It's not a bug thankfully, but you've discovered a rather non-intuitive interaction among the random streams. Here's what's happening: Since your .vsc varies the req input mean size, but not the random seeds, I'd normally expect your graph for the uniform draws (and probably the others, though I hav...

That should do it.

... or not. Looks OK to me.

What's in your .vsc sensitivity control file?

Ahh ... now I get it.

Are the "average" results from your word doc from a Monte Carlo sim, with different seeds?

Got it - I have to hop on a plane shortly but will have a look ASAP.

The uniform random results look particularly wrong, in that they should all have the same ranges, means & variances, unless the parameters (other than the seed) differ. I've tested sequences of 2 billion uniform random draws with the NIST test suite, and they were OK. I think I understand what y...

For a few special situations the SINTEG function may be useful - see the Help system.

There's a lengthy discussion of this here http://www.ventanasystems.co.uk/forum/viewtopic.php?f=26&t=1128 The basic point is that you need to express why the stock can't go negative, i.e. how the "physics" of the situation limits its outflows when the stock nears 0. The most common sit...

Without the corresponding model, I'm not really sure what I'm seeing here. If you're running the model with a 1-day time step, it's likely that the issue is that the integration through a stock imposes a 1-day lag (at minimum). You might be able to resolve this by changing the integration method to ...

I think you want something more like this:

I'm sure there's a way to do what you're after, but it's hard to tell without some more information. - var1 and var2 need real names - what do they represent? - all variables should have units of measure - it's unconventional to have causal arrows directly influencing levels; arrival-discharge+8+ va...

Oops. Duh. Sorry!

It did change. See http://www.vensim.com/documentation/sensitivity.htm

I should add that this requires arrays for the seasonal bins. If you're only smoothing, or forecasting at integer multiples of the seasonal period, you could get by with a DELAY FIXED instead of the array, which would permit making this into a macro.

Here it is. I couldn't find my original, so I had to reconstruct it. This is similar to https://www.otexts.org/fpp/7/5 , but that's discrete time and dimensionally inconsistent unless you add a bunch of implicit time constants. I think my approach is mathematically very similar, if not identical, wh...

I'm not sure I follow the question. In this structure, people are conserved, so there's no double counting. If the issue is preventing a person who has become addicted and then recovered from becoming addicted again, that actually sounds like a very realistic situation. However, you could model that...

I presume that the exact calendar age of people in the model is not the feature of greatest interest, so I would use explicit stocks and flows, with a fairly large interval of a number of years (maybe ten or twenty, though I don't know what your model time horizon is). It's much easier to add elemen...

You can't do it with the DELAY CONVEYOR function, but you can do it with standard stocks and flows. The difference (possibly) is that the infinite-order delay functions have an internal number of stocks equal to TIME STEP*DelayDuration, which could be a lot in some cases (hard to draw). If you expla...