Ventana software support forum

Thank you Bob OK, so for a model with time step = 1 week and data every 4 weeks ; where the model's calibration analysis covers the 25 datum point observations when FINAL TIME = 100 autocor1 is the correlation of error[t] vs error[t-4] autocor2 is the correlation of error[t] vs error[t-8] autocor3 i...

When doing a calibration run, the REP file presents the following statistics; Autocor1, Autocor2, Autocor3 and Autocor4 The other statistics presented in the REP file are self-explanatory but I would not want to assume these are one thing when in fact they may be something else. I could not find any...

bathtub volume of water = INTEG( net flow into tub , inital tub volume of water) If the tub is empty at start then initial level = 0 , if faucet is shut and drain plug is in; net flow = 0. Open faucet and tub fills at net flow rate, open the drain at the same time and the net flow into tub = inflow ...

Good day JJ; I should re-visit the ‘Digest’ software you referenced. Thank you for the heads up. A good exercise akin to your ‘report’ is to slog through a reduced form version of the model ( dx = Ax + c ; A = matrix , others arrays and x= model stocks ) that one encounters on the way to eigenvalue ...

Response to JJ’s previous post; JJ says: “Is a parameter unchangeable exogenous or endogenous?” Good point; one could argue that any model ‘item’ not both influencing another model variable and influenced by another model ‘item’ could be considered ‘exogenous’ in some sense. JJ says: “But what makes...

Good day JJ, i have been working on a model for a long time and was doing a review by listing each Vensim's View variables in the following categories for each view; 'endogenous inputs', 'endogenous outputs', 'key model variables' , 'exogenous inputs' and ... 'exogenous outputs'. As soon as i looked...

Why is it that people seemingly have exogenous outputs but models never do ( well unless it is the trivial example of exogenous-in-exogenous-out ) ?

Your post provides useful guidance in these stressful times. Do you think if more people look at these “value propositions” it will lead them to System Dynamics stock-flow modeling ( from Systems Thinking ) and to “strategic decision-making” from the posted “value propositions” ? The risk here thoug...

If you can discuss the need for brushing up your calculus with someone with solid SD expertise ( I don't consider my expertise as being 'solid' ) you might find its not crucial. Its amazing what 'calculus' insights you can get from simply diving in and buidling your own models; carefully scrutinizin...

At the risk of being moot; and ignoring for the moment the details of 'Lean' beyond the notion of efficient use of resources, you can't go wrong with two books; Sterman's "Business Dynamics" and Kim Warren's "Competitive Strategy Dynamics"; give yourself a few years to get going ...

Thank you Bob.
Appreciate the guidance.

Mike

On August 24, 2004 Ventana Systems sent the following e-mail about MSFT C++ compilers; Microsoft Visual C++ Toolkit 2003 --------------------------------- Microsoft has chosen to make its C++ compiler engine available for free. If you are using Vensim DSS and want to speed up your simulations by com...

THANK YOU; I didn't realize the need for the extra variable assignment.

Regards,

Mike

attached model

attached xls

couldn't attach word doc with Vensim graphs to illustrate problem; the spreadsheet data is 4 annual year end data points in a 16 year, monthly time step simulation ; expected :LOOK FORWARD: to show 192 data points where it only replicated the 4 points fed in ?

Given the following equations; "spreadsheet data 00-03" := GET XLS DATA( 'data.050204.xls' , 'vensim' , 'xls_time' , 'xls_named_range '\ ) ~ $ ~ | test data LOOK FWD :LOOK FORWARD::= "spreadsheet data 00-03" ~ $ ~ ~ :SUPPLEMENTARY | For the above data equations I had expected ‘te...

for growth = ( aux-t - aux-t-1) / aux-t-1
then use

lastaux = DELAY FIXED(aux,1,aux) ~~|
auxgrowth = (aux - lastaux) / lastaux ~~|

using xidz(...) or such as called for

Thank you; I'll resolve this myself or get some local talent to resolve this compilation issue.
Good day.

Mike

Attachment uses different colored fonts to make it more readable .... Using Vensim External Functions via the freely downloadable Visual C++ Toolkit 2003. Got the following from Vensim e-mail 08/24/04 concerning Vensim Version 5.4a update: Microsoft Visual C++ Toolkit 2003 --------------------------...

THANK YOU RAFAEL

Mike

If one needs to take a pre-existing stock-flow model and represent it in causal loop diagram form are there alternatives to simply re-creating a separate model, making the levels auxilliaries and adding all connection polarities ?

Thoughts, experiences appreciated.

Mike

I forgot about the Control Panel setting. Appreciate the guidance! Good day. Mike

WinZip said "Cannot open file; it does not appear to be a valid archive; if you downloaded the file; try again " or something to that effect. Never encountered this before ? I tried downloading again to no avail. Regardless ; appreciate the guidance. If I can help; let me know. Regards, Mi...

I tried to do this but the graph came up empty when I tried to use decimal year as the graph's x-axis; it works fine using time (monthly ) as x-axis ?????? how can I graph monthly variables with x-axis showing 1960 .... 1970 .... 1980 ....