Search found 107 matches
- Mon Nov 08, 2010 6:19 am
- Forum: Vensim
- Topic: Prevent negative stock
- Replies: 4
- Views: 8882
- Tue Oct 05, 2010 6:22 am
- Forum: Vensim
- Topic: Unit Error: Mantissa of ^ must be dimensionless
- Replies: 3
- Views: 3222
- Thu Sep 23, 2010 7:30 pm
- Forum: Vensim
- Topic: Simple Optimization
- Replies: 6
- Views: 4530
Simple Optimization
Dear Giovanni, Attached is my model... on the same lines of both what JJ and Tom were saying. I created a penalty function that measures the square of the difference between desired and actual inventory. We then cumulate this difference and normalize it in the form of an objective function to give y...
- Tue Sep 21, 2010 4:34 pm
- Forum: Vensim
- Topic: Discrete Processes Stella Vs Vensim
- Replies: 0
- Views: 3172
Discrete Processes Stella Vs Vensim
Recently, there have been many posts about discrete functions and also references to the numerous books/examples on management written using Stella's discrete processes. A few years ago, I created a Vensim model (Based on the "grocery model" Chapter 4 in Bruce Hannon's: Modeling Dynamic Ec...
- Thu Sep 16, 2010 5:50 pm
- Forum: Vensim
- Topic: How to allocate without allocation functions?
- Replies: 4
- Views: 2843
There was a question in the thread some time ago:
http://www.ventanasystems.co.uk/forum/v ... php?t=3997
and
http://www.ventanasystems.co.uk/forum/v ... php?t=4020
Best Wishes,
Karan
http://www.ventanasystems.co.uk/forum/v ... php?t=3997
and
http://www.ventanasystems.co.uk/forum/v ... php?t=4020
Best Wishes,
Karan
- Fri Sep 03, 2010 8:51 am
- Forum: Vensim
- Topic: Error on Symultaneous equation
- Replies: 7
- Views: 5780
- Sat Jul 31, 2010 6:03 am
- Forum: Vensim
- Topic: S-shaped growth with maximum and minimum absolute points
- Replies: 2
- Views: 2255
- Mon Jul 19, 2010 6:58 pm
- Forum: Vensim
- Topic: TREND function and Vensim PLE
- Replies: 7
- Views: 5296
Macros
Dear Lukas, As for the macros, you have to go into the text editor for Vensim (under view "As Text") and insert the macro code in the equation set. For example, here is a macro which demonstrates (one possible) way to find the first derivative of a variable: :MACRO: firstderiv(input,dt) fi...
- Mon Jul 19, 2010 6:35 pm
- Forum: Vensim
- Topic: TREND function and Vensim PLE
- Replies: 7
- Views: 5296
- Thu Apr 29, 2010 5:46 am
- Forum: Vensim
- Topic: Optimization error
- Replies: 4
- Views: 3385
- Wed Mar 10, 2010 5:31 pm
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
- Mon Mar 08, 2010 8:06 am
- Forum: Vensim
- Topic: data storage
- Replies: 8
- Views: 4915
- Thu Mar 04, 2010 10:02 am
- Forum: System Dynamics Discussion
- Topic: Eigenvalue and Eigenvector Analysis of Dynamic Systems
- Replies: 7
- Views: 6261
- Thu Mar 04, 2010 6:12 am
- Forum: System Dynamics Discussion
- Topic: Eigenvalue and Eigenvector Analysis of Dynamic Systems
- Replies: 7
- Views: 6261
Hi JJ, I'm glad you asked! I have an organization called EarthSafe with which I try to promote systems thinking in sustainable development practice. To be honest, the only reason I started EarthSafe was as an excuse to devote all my time to learning everything I possibly can about the science of sys...
- Wed Mar 03, 2010 2:10 pm
- Forum: System Dynamics Discussion
- Topic: Eigenvalue and Eigenvector Analysis of Dynamic Systems
- Replies: 7
- Views: 6261
hmm...apparently the forum won't upload my .zip files (745kb in size). You can download them from the following link: http://www.earthsafeonline.com/Papers_Research/DomLoops.zip JJ - my work is research oriented, in particular trying to model various issues of socio-economic relevance in developing ...
- Wed Mar 03, 2010 10:27 am
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
- Wed Mar 03, 2010 7:43 am
- Forum: System Dynamics Discussion
- Topic: Eigenvalue and Eigenvector Analysis of Dynamic Systems
- Replies: 7
- Views: 6261
- Wed Mar 03, 2010 7:42 am
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
- Wed Mar 03, 2010 7:38 am
- Forum: System Dynamics Discussion
- Topic: Eigenvalue and Eigenvector Analysis of Dynamic Systems
- Replies: 7
- Views: 6261
Eigenvalue and Eigenvector Analysis of Dynamic Systems
Lately, I have had a little time to catch up on some SD reading! It seems there are two interesting methods out there for calculating dominant feedback loops in a system; David N. Ford's is the first, in which changes in the behavior of a loop's "atomic" pattern (calculated by observing th...
- Mon Mar 01, 2010 11:07 am
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
- Mon Mar 01, 2010 10:17 am
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
Thanks a lot JJ, yes it was just a trial to see if I could get fulfill a time constraint as well. I was just reviewing Geoff Coyle's book (the section on optimizing) he defines the objective function as a level of a penalty, e.g. pen.k = pen.j +dt*(Desired Population - Population)^2: pen0 = 0. Then ...
- Mon Mar 01, 2010 7:44 am
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
- Sun Feb 28, 2010 8:47 pm
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
- Sun Feb 28, 2010 6:36 pm
- Forum: Vensim
- Topic: Optimize for particular value at a specific time
- Replies: 15
- Views: 7897
Optimize for particular value at a specific time
Greetings!
Please see the sample model I made; how can I optimize parameters to fulfill a value constraint and also a time constraint? I would like the population to be near 300 by time 20 (months).
Thanks!
Karan
Please see the sample model I made; how can I optimize parameters to fulfill a value constraint and also a time constraint? I would like the population to be near 300 by time 20 (months).
Thanks!
Karan
- Tue Feb 16, 2010 7:13 am
- Forum: Vensim
- Topic: Optimize Lookup
- Replies: 7
- Views: 4594