Ventana software support forum

reservoir.mdl Here's an alternate way to arrange things, using an array of lookups and VECTOR SELECT to choose the active series. Rather than a tabbed array, you'd supply an array of lookups (see the subscripted version of the GET...LOOKUPS example model in the help system). There are probably othe...

I haven't had a chance to check the code, but I suspect what it's doing is essentially using the c %g format convention, which chooses between a direct decimal or scientific notation, whichever is shortest. http://www.cplusplus.com/reference/cstdio/printf/ . Whether you get 0.9973 or 4.621e9 will de...

Now that I think about it, I'm guessing that you've written, smoothed x = SMOOTH( x, 8 ) where 8 (or whatever) is the smoothing time. The problem is that Vensim doesn't know the units for 8, so it assumes dmnl. Make the 8 a parameter, which also exposes it to sensitivity analysis, and give it units ...

Can you post an example?

You could modify the equation to suppress the error. Two possibilities: 1. Add an extra point to the lookup, at FINAL TIME or beyond. It won't get used, but will prevent running out of bounds. 2. use MIN(Time, 9) rather than Time as the input to the lookup. You probably also want to make the "9...

One possibility is to regard price as a stock that adjusts in response to pressures from supply/demand balance.

I see what you mean. The long tail of the exponential distribution of servicing patients seems weird compared to intuition about the actual process. However, the solution, MIN(max patients seen,patients waiting), fails two other reality checks. First, if TIME STEP <> 1, it doesn't work; for continuo...

Other ways to look at this: 1. dimensional consistency equating patients seen = MIN(max patients seen,patients waiting) mixes items with units of people and people/minute. 2. implicit time constants patients seen = MIN(max patients seen,patients waiting) and patients seen = MIN(max patients seen,pat...

However, eggs are not an outflow from the stock of chickens (though of course, in a literal sense, eggs do flow out from chickens). This is because laying of eggs does not reduce the stock of chickens (at least if chickens are measured numerically). Normally, you'd have a stock of parent chickens, w...

Looking at parent chickens, you might write: parent chickens = INTEG( maturing - age culling - disease death rate - productivity culling, initial chickens) where maturing, age culling, etc. are inflows and outflows. This would appear on the diagram as a separate flow pipe for each process. If that g...

Here's an alternate implementation, with units:

Generally, if you use the : DATASET key with a wildcard like *2 (for the second run), nothing will be shown if only one run is loaded, so you don't need to know in advance what is available.

If you mean the crosshatch delay mark on arrows, right-click the arrow and check the "delay" box.

I don't think it's possible to perform mathematical operations on the two runs. An alternative, if these represent something like a "base" and "policy" scenario, is to subscript the entire model with a scenario dimension, e.g. scenario : base, policy, so that both runs happen at ...

It sets an absolute limit on the number of simulations in an optimization.

I suspect that what's happening is as follows: During simulation, there's slight imprecision that causes the double representation of the variable to be less than 0, but with an absolute value smaller than the smallest float. When the values are stored to the vdf, which is single precision, rounding...

You might also take a look at the PULSE, STEP and PULSE TRAIN functions for alternatives to the test input with IF THEN ELSE>

Not that I know of, but you can use the percentile() function in Excel to calculate intervals.

I think there's a 5th option, which is using the QUEUE ATTRIB functions, where (one of) the attributes is the time of entry into the chain. That only works if the process is really FIFO, which isn't the case for conveyor leakage unfortunately. Otherwise, I tend to favor the SHIFT IF TRUE approach - ...

See also the last answer in this thread: http://www.ventanasystems.co.uk/forum/v ... f=2&t=5283

Right - rather than using

carp growth lookup(time)

just use

carp growth lookup( MODULO( time, months per year ) )

with months per year = 12.

OK - now I understand the problem - I'll have to ponder a bit. We have a nice solution for this in future Vensim, but it won't be available for a while.

Differential time steps would be much harder to implement than it sounds ... why do you need it?

What parameters are you using in the model (including TIME STEP)? For me, the linked SimpleConveyorModelCorrTF1.mdl works fine with FractionEventuallyLeaking = 1. Extremely high leak rates do beg the question, why bother with a stock or conveyor, but I agree that the tool should be robust to such ex...

Generally, that shouldn't matter. You could try renaming them (e.g., vensim.inix) temporarily - Vensim will start with default settings if the .ini is missing. But the effect of that should be the same as a reinstall that resets the .ini, so that's probably not the problem. Tony's test - whether you...