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## NetLogo User Community Models

WHAT IS IT?

This is an adaptation of the "Turtle Ecology" model from the Resnick "Turtles" book.

HOW IT WORKS

After the initial setup when food and turtles are randomly placed around the screen, the 'go' procedure runs forever. Each period the turtle moves, then eats, then some die, then some reproduce, then the food grows, and finally the plot is added to.

HOW TO USE IT

Set the values in the sliders, click on the Setup button and then click on the Go button to start (and then stop) the execution of the model.

init-num-of-turtles: The number of turtles when the model starts executing.
bearing-change: Each period the turtle resets its heading. If 'bearing-change'
is 30, then it can change by 30 degrees to the left or 30 degrees to the right.
Thus, the smaller this value, the more the agents will go in straight lines.
reproduction: This is the minimum energy level that an agent must have for it to
reproduce.
initial-energy: This is the maximum energy value that an agent can have at the
beginning of the simulation. The actual value is a random value between 0 and
initial-energy.
inverse-food-rate: The proportion of the patches that will grow back per period
is 1/inverse-food-rate.
inverse-food-setup: The proportion of the patches that start out with food
is 1/inverse-food-setup.

NETLOGO FEATURES

This works somewhat differently than the StarLogo version described in the book. The book version uses "demons" while this version uses the "go" procedure to step through each of the different actions that a turtle does each period.

CREDITS AND REFERENCES

This model was developed at the MIT Media Lab. See Resnick, M. (1994) "Turtles, Termites and Traffic Jams: Explorations in Massively Parallel Microworlds." Cambridge, Ma: MIT Press, pp. 88-95. Scott A. Moore (samoore@umich.edu) of the University of Michigan Business School adapted this model to NetLogo.