Ventana software support forum

It sounds to me like you're actually asking about the objective function. In a calibration optimization, it is the sum of squared residuals, by whatever weights you select. (If you're using Kalman filtering, it's the log likelihood, more complex but same general idea). In a policy optimization, it's...

As a rule, the left and right side have to have the same number of subscript ranges. They key here is that in example2[aircraft]=example1[aircraft,p1]+1 p1 is a single _element_ of probabilities, not a _range_. Therefore no corresponding range needs to exist on the left side. The left and right side...

Can you create a copy of the structure that generates the base run value, so that you have an independent version, outside the logic that will be affected by the RC? Or is everything too endogenous?

Another obvious candidate for a functional form is a polynomial of time, e.g.

decision = constant + a*time + b*time^2 ...

A much better option, if possible, is to create a feedback rule, e.g.

decision = constant + a*level_1 + b*level_2 ...

There must be something funny about the server MIME types because the file downloads without an extension, so you need to add the .mdl to the file name. There appear to be other syntax errors as well. For example, land rent[land use type]= soybean land rent[Soybeans], corn land rent[Corn], ... needs...

You can use ALLOCATE AVAILABLE with variables. The issue in the model posted on 1/15 is that attractiveness[Corn,pprofile]= 3,corn priority,0,0 ~~| mixes constants and auxiliaries. You need to reorganize your subscript equations, for example as: attractiveness[land use type,ptype] = land use ptype~~...

What you're specifically after would be something like the following, I think:

Cum Sales = INTEG( sales - outflow, 0 )
outflow = DELAY FIXED( sales, time to cumulate, 0)
time to cumulate = 3

The continuous version would have
outflow = Cum Sales/time to cumulate

Tom

Hi Bob - I think you mean GET XLS LOOKUPS ? - Tom

You can create a vector lookup using subscripts. It's not as convenient, but works. Here's one approach (not necessarily the best way to do the interpolation, but it works): interval weight[xNext]= MAX(0,MIN(1, (x input-x vals[xPrev])/(x vals[xNext]-x vals[xPrev]) )) ~~| interval weight[x1]= 1 ~ ~ |...

Appropriate statistics for estimating dynamic models are described in Fred Schweppe's Uncertain Dynamic Systems , which is unfortunately out of print. David Peterson described the approach for SD in his thesis, http://dspace.mit.edu/handle/1721.1/27424 , which is more or less the basis of the implem...

It may be possible to solve this problem using the FIND ZERO function to find a vector of prices that achieves some equilibrium condition. However, I agree with Bob that it would be better to be explicit about the dynamics. I would expect that you'd want stocks of land in each category - perhaps exp...

You might check out Chapter 5 of the Road Maps series, which includes 2 articles on delays. http://sysdyn.clexchange.org/road-maps/rm-toc.html

Originally posted by Monte Hi JJ, This definition might impress you: System dynamicist n. 1 a person who works in, or is skilled in the system dynamics technique. 2 a person who holds a Ph.D. degree in System Dynamics. People with a PHD are surely system dynamicists. Others who use SD effectively a...

"To my opinion all these models are far too complicated and loose all their power of influence by adding too many details. I can hardly imagine a politic being influenced by such complicate models and the paradox is that these big models being not able to influence political decisions, the poli...

Hi JJ, Bob pointed out this thread to me. Based on a quick look at the 03 version, most of the out-of-bounds messages appear to be of little consequence, because they occur in places where the table function is already at a logical extreme or 0 slope anyway, so the default behavior is appropriate. T...