1. An introduction to Netlogo agent-based software
Brian Dermody

2. What is an agent? An agent is an individual It has attributes
Person, plant, electron etc.
It has attributes
Happy, wilted, charged etc.
It performs actions
Buy/sell, grow, radiate etc.
It exists in an environment
Market, ecosystem, atom etc.
Agents are often different
Interactions among agents and their environment bring about emergent behaviour/ patterns

3. Emergence
Small scale interactions among agents and their environment bring about higher-level emergent patterns
Simple – complex
Cross-scale feedbacks

4. Netlogo
Netlogo is the most widely used agent-based modelling environment in both education and research.
Netlogo is written mostly in Scala, an object-oriented language, with some parts in Java.
Netlogo consists of a Graphical User Interface (GUI) frontend with code on the backend.
GUI consists of buttons, sliders, graphs which can be linked with the code.
Here start with a blank model.

6. Netlogo
Netlogo is the most widely used agent-based modelling environment in both education and research.
Netlogo is written mostly in Scala, an object-oriented language, with some parts in Java.
Netlogo consists of a Graphical User Interface (GUI) frontend with code on the backend.
GUI consists of buttons, sliders, graphs which can be linked with the code.
Netlogo runs sequentially, parallel not possible: Disadvantage!
Here start with a blank model.

7. Netlogo
Agents (Turtles in Netlogo speak) interact with environment and each other
The environment comprises of patches
Grid-based data

8. Netlogo
Agents (Turtles in Netlogo speak) interact with environment and each other
The environment comprises of patches
Grid-based data
Supports multi-agent networks
Check model library for examples
So one of the classic examples of emergence is the segregation model. The idea behind this model was how people areas arise with in cities with people of different ethnicities. So-called ghettoization of cities. The author, Thomas schelling figured it was just an inevitable outcome of the desire to be close to a certain amount of people from the same ethnicity. He figured that ghettos within cities were an emergent property of of people wanting to live close to people of the same ethnicity. Depending on the intolerance for other ethnicities, the more ghettoized a city would become
So the way this model works is that each individual has a certain desire about the number of people they want the same around them. So for example, they want that at least 20% of their immediate neighbours are of the same ethnicity. If that is not the case they move somewhere else. And that continues. The more intolerant they are (i.e. the more of their own ethnicity they desire) the more ghettoized the city becomes.
observer> ask turtle 0 [show count links]
observer> ask turtle 0 [show count my-links]
observer> ask turtle 0 [set color red]

9. Netlogo attributes
Global attributes are "global" because they are accessible by all agents and can be used anywhere in a model.
Agent/agent-set attributes: accessible by agents
Patch attributes: accessible by patches
Link attributes: accessible by links and node agents (for network models)

10. Tutorial
Go to uu.nl/clue and download the text file.

11. Tutorial Open Netlogo and paste the provided code under the code tab
The model doesn’t work? – We need to provide links between frontend and the code

12. Tutorial Open Netlogo and paste the provided code under the code tab
The model doesn’t work? – We need to provide links between frontend and the code
Use the check to see where the problems lie
You code relates to frontend controls such as buttons and sliders. You need to add these

13. Tutorial
Add a slider that allows you to flexibly set the number of “vulture” agents (min 0, max 50)
Add chooser for roost-dispersed (10, 50)
Add slider that allows you to flexibly set the number of “carcass” agents (min-0, max 50)
You need to add a “setup” and “go” buttons
Set go as “forever”
Change area of environment to 30*30 with patch size 10

14. Agent-based model of vulture foraging
Vultures
Scavengers
Soaring flight
Vulture foraging
Food is spatially and temporally ephemeral
Large enough to feed more than one forager
Food becomes easier to see when it is found by others
Activity at the carcass
Rapid descent of other vultures
Vultures roost communally
Research Questions
What is the importance of the roost?
Do vultures form groups?

15. Coordinated movement in animal groups
In order to give our vultures in our model the ability to react to other vultures we assigned them with 3 rules which are the basis for group behaviour in a range of animals.
Animals that form highly cohesive groups are proposed to do so using three simple rules. These can be thought of in terms of decision circles around the animal and depending on where other animals fall within those spheres the decisions the animal makes will be different. For example if another agent enters the red ring of this agent it will move away, if
Couzin et al. (2005)

16. Assignment
Add ZoR, ZoO and ZoA sliders to the Netlogo frontend and link with code on coordinated movement (0-5 with increment of 0.1)
What type of coordinated movement do you see for different combinations of the 3 sliders?

17. Assignment
Add ZoR, ZoO and ZoA sliders to the Netlogo frontend and link with code on coordinated movement
What type of coordinated movement do you see for different combinations of the 3 sliders?

18. More questions? Netlogo dictionary Netlogo models library
Simply right-click command
Netlogo models library
Adjust existing models to meet your needs
Netlogo user community forum
Usually answers within 1 day