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