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Modelling with Vensim 101: Basics

A quick introduction to System Dynamics Simulation using Vensim.

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Modelling with Vensim 101: Basics

  2. 2. First: System dynamics… How is my inventory policy affecting my cash flow? Is an ERP the ‘answer’ to our problems? How can people respond to a tax increment? It’s all about understanding the structural causes that affects the system
  3. 3. Stocks People Goods Rabbits Meters Gallons Pollution RABBITS Whatever you see when picturing it… those are stocks! Let’s take a mental photo of… let’s say a bunny colony
  4. 4. Stocks are like a glass… they fill up… or drain out…
  5. 5. FLOWS People/year Goods/Shift Rabbits/Month Meters/Second Pollution/year Unit/Time How do you fill up/drain out that glass?
  6. 6. Fills it Rabbits Births Deaths Drains it Warning! Rabbits in the area
  7. 7. If it’s not a stock… if it’s not a flow It‘s either an auxiliary variable or a constant.
  8. 8. Population Dynamics Conceptual Model Or… Stock and flows model
  9. 9. Our first model Can you picture it? What’s the main stock here?? What’s feeding that stock? What are the flows? Let’s go to a warehouse… a quite simple one
  10. 10. Our first model: The bones It should look something like this:
  11. 11. Let’s build that up!!! Flow
  12. 12. Let’s build that up!!!
  13. 13. Now some ecuations
  14. 14. Performance Indicators
  15. 15. Simulation!!!
  16. 16. Results
  17. 17. Mario Andrés López