Biology Reference
In-Depth Information
Exercise 4.10.
This exercise considers the sensitivity of outputs to the choice of
the preference-level of each turtle to have its neighbors be the same color. Return to
the setting of 1000 turtles on the grid. By the way, it will be helpful here to notice that
the simulation only stops if every turtle is happy. If you want to stop the simulation
yourself, just click on the go button.
a.
Is it possible to choose a
%-similar-wanted
level at which some turtles are not
happy at the end? If so, about what value of
%-similar-wanted
seems to be the
breaking-point between all-happy and some-unhappy turtles? Also, what is the
corresponding end percent of like-colored turtle neighbors?
b.
Without running any simulations, conjecture what you think would happen if the
turtles were more crowded. How would the results above likely change if we fit
2000 turtles into the same space?
c.
Repeat the simulations and analysis from part (a) for the problem with 2000
turtles. Did any of the results surprise you?
The remaining exercises provide an introduction to the syntax within the NetLogo
code. Click on the “Procedures” tab. The commands following the phrase
to setup
in the code for the simulation tell NetLogo what to do when the user clicks the setup
button. In this case, we see:
Ask n-of number patches
[sprout 1
[set color red]] Note that number has been defined
with a specific numerical value elsewhere in the code.
Exercise 4.11.
Highlight
sprout
and click on the Help menu to look this up in the
NetLogo Dictionary. What does the command
sprout 1
accomplish?
Exercise 4.12.
Look up the phrases
n-of
and
set color
similarly. What do the
three lines of code above accomplish all together?
Exercise 4.13.
How does the code determine if a turtle is happy?
Exercise 4.14.
How far can a turtle move in a given step to try to find
happiness?
Exercise 4.15.
Did the assumption of how far the turtles could move have a big
influence on results? Would any of the outcomes of this simulation change if the turtle
could move as far as 20 units each time? Make this change, and repeat a few of your
experiments.
Exercise 4.16.
Change the code so that there are only a tenth as many green turtles
as red turtles and repeat some of your experiments. Does this make a difference?
Exercise 4.17.
What are the agents in this model? What characteristic(s) does each
agent have? What are the rule(s) governing the system?
Exercise 4.18.
Project: Modify the model code so that there are three colors of
turtles. Do any of the conclusions change in this situation?
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