Post on 18-Dec-2014
description
MODELING WITH VENSIM 101: BASICS
First: System dynamics…
It’s all about understanding the structural causes that affects the system
How is my inventory policy affecting my
cash flow?
How can people respond to a tax
increment?
Is an ERP the ‘answer’ to our
problems?
Stocks
Whatever you see when picturing it… those are stocks!
Let’s take a mental photo of… let’s say a bunny colony
People Goods Rabbits Meters Gallons Pollution
RABBITS
Stocks are like a glass… they fill up… or drain out…
People/year Goods/Shift Rabbits/Month Meters/Second Pollution/year Unit/Time
FLOWS
How do you fill up/drain out that glass?
Births Deaths
Rabbits
Fills it
Drains it
Warning!
Rabbits in the
area
If it’s not a stock… if it’s not a flow It‘s either an auxiliary variable or a constant.
Population Dynamics
Or…
Stock
and
flows
model
Conceptual
Model
Our first model
Let’s go to a warehouse… a quite simple one
Can you picture it? What’s the main stock here??
What’s feeding that stock? What are the flows?
Our first model: The bones It should look something like this:
Let’s build that up!!!
Flow
Let’s build that up!!!
Now some ecuations
Performance Indicators
Simulation!!!
Results
Mario Andrés López
mlopez0301@gmail.com