Unit One: Lesson 2 - Modeling And Simulation Activity Guide
Name(s):Siena Stephenson Period:4A Date:9/12/17
Activity Guide - Modeling And Simulation
Overview
In this activity, you will learn to use NetLogo Web, a free web-based programming environment for
simulation. The site comes with hundreds of pre-defined models of things like the spread of disease, the
effect of clouds on global warming, etc.
You will…
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NetLogo models are made by scientists and computer programmers. Scientists come up with models of
how things behave - like people at parties, trending topics on the Internet, oil spill spread, sun rays
through the earth's atmosphere, and many many more. Computer programmers (who often are the
scientists themselves!) write code in the NetLogo language to have elements called turtles in the NetLogo
world behave like the things they are modelling (e.g. people, Internet topics, oil, sun rays, etc).
Learn to control NetLogo models with buttons, speed slider, sliders and switches
Learn to gather information of NetLogo models with plots and monitors
Explore and experiment with models like the Wolf Sheep Predation
You will submit...
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Completed activity guide
Activity Steps
Step 1: Wolf Sheep Predation Model
There are many models that have been created and are available in NetLogo Web - a version of NetLogo
that runs entirely in the browser - you don't have to download any software. Open the Wolf Sheep
Predation model as an example.
When you first open the model, you will notice that the view (graphical display of the agents in the model)
is empty (all black). To begin the model, you will first need to set it up.
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DO THE FOLLOWING:
➔ Click the setup
button.
button.
➔ To stop the simulation, click the go
button.
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➔ To start the simulation, click the go
The Interface tab will fill up with lots
of buttons, switches, sliders and
monitors. These interface elements
allow you to interact with the model.
Buttons are blue; they set up, start,
and stop the model. Sliders and
switches are green; they alter model
settings. Monitors and plots are
beige; they display data.
Now that you know how to setup and run the simulation, you
should learn what the model is actually about.
DO THE FOLLOWING:
➔ Click on the Model Info tab at the bottom of the screen.
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
As you can see, this offers guidance and insight into the model, how to run it, and some things to try.
Answer the following question in the box below about the Sheep Wolf Predation model.
Let’s Write!
In your own words, describe what the model is.
Hint: Look at Model Info section.
This model shows the stability of predator-prey ecosystems.In A system is stable if it tends to maintain
itself over time, despite fluctuations in population sizes.
Step 2: Controlling The Model With Buttons
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When a button is pressed, the model responds with an action. A button can be a once button, or a forever
button. You can tell the difference between these two types of buttons by a symbol on the face of the
button.
Once buttons don't have
Most models, including the Wolf Sheep Predation, have a one
the arrows, like this:
button called set up and a forever button called go. Many models
also have a one button called go once or step once which is like go
except that it advances the model by one tick (time step) instead of
Once buttons do one action
over and over. Using a one button like this lets you watch the
and then stop. When the
progress of the model more closely.
action is finished, the
button pops back up.
Stopping a forever button is the normal way to pause or stop a
model. After pausing, you can make it resume by pressing the button again. (You can also stop a model
with the Halt item on the Tools menu, but you should only do this if the model is stuck for some reason.
Using Halt may interrupt the model in the middle of an action, and as the result the model could get
confused.)
DO THE FOLLOWING:
➔ Experiment with setup and go buttons to run the Wolf Sheep Predation model several times.
Let’s Write!
the
Do you ever get different results if you run the model several times with
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same settings?
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When I stopped the simulation at 400 ticks there was 170 sheep, 70 wolves and 221 grass. The second
time I tried it with the same settings after 400 ticks I ended up with 193 sheep, 64 wolves and 216
grass. I noticed that the number are close each time.
Step 3: Controlling Speed With Speed Slider
The speed slider allows you to control the speed of a model, that is, the speed at which turtles move,
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Foreve
arrows
corners
Forever
action o
When y
to stop,
again. I
current
back up
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
patches change color, and so on.
When you move the slider to the left, the model slows down so there are longer pauses between each tick
(time step). That makes it easier to see what is happening. You might even slow the model down so far as
to see exactly what a single turtle is doing.
When you move the speed slider to the right, the model speeds up. NetLogo will start skipping frames,
that is, it won't update the view at the end of every tick, only some ticks. Updating takes time, so fewer
view updates means the model progresses faster.
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Note that if you push the speed slider well to the right, the view may update so infrequently that the model
appears to have slowed down. It hasn't, as you can see by watching the tick counter race ahead. Only the
frequency of view updates has lessened.
Step 4: Adjusting Settings With Sliders And Switches
A model's settings let you explore different scenarios or hypotheses. Altering the settings and then
running the model to see how it reacts can give you a deeper understanding of the phenomena being
modeled.
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Switches and sliders give you access to a model's settings. Here are the switches and sliders in Wolf
Sheep Predation:
Let's experiment with their effect on the behavior of the Wolf Sheep Predation model.
DO THE FOLLOWING:
➔ Click the setup
button.
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
➔ Click the go
button.
➔ Let the model run about 100 ticks (the tick count is shown above the view).
➔ Click the go
Let’s Write!
button to stop the model.
What happened to the sheep over time?
Over time (100 ticks) the sheep definitely doubled in numbers. There was 366 sheep after the 100 ticks
was over and only 214 wolves.
Now see what happens to the sheep if you change a setting in the Wolf Sheep Predation model.
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DO THE FOLLOWING:
➔ Turn the grass? switch on.
➔ Click the setup
button.
➔ Click the go
button.
➔ Let the model run about 100 ticks (the tick count is shown above the view).
Turning the grass? switch on will affect the outcome of the model. With the switch off, the amount of grass
available always stayed the same. This is not a realistic look at the predator-prey relationship; so by
setting and turning on a grass regrowth rate, we were able to model all three factors: sheep, wolf and
grass populations.
DO THE FOLLOWING:
➔ Turn the grass? switch on.
➔ Click the setup
button.
➔ Click the go
button.
➔ Re-run the simulation for 100 ticks (the tick count is shown above the view).
Let’s Write!
Was the outcome the same as your previous run of the simulation? Why?
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No the outcome was not the same. With the grass switch on there was more sheep eating the grass
then more wolves eating the sheep. Overall there was 182 sheep, 66 wolves and 206 grass.
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
Another type of setting is called a slider. While a switch has only two values, on and off, a slider has a
whole range of numeric values. For example, the initial-number-sheep slider has a minimum value of 0
and a maximum value of 250. The model could run with 0 sheep or it could run with 250 sheep, or
anywhere in between. Try this out and see what happens. As you move the marker from the minimum to
the maximum value, the number on the right side of the slider changes; this is the number the slider is
currently set to.
Let's see what would happen to the sheep population if there were more sheep and less wolves initially.
DO THE FOLLOWING:
➔ Turn the grass? switch off.
➔ Set the initial-number-sheep slider to 100.
➔ Set the initial-number-wolves slider to 20.
➔ Click the setup
button.
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➔ Click the go
button.
➔ Let the model run for about 100 ticks.
Try running the model several times with these settings. Once you are finished, answer the following the
questions.
Let’s Write!
What happened to the sheep population? Why?
After the 100 ticks the sheep population increased into 2214 while the wolf population was 119. I think
this happens because the individual sheep population was slid up 100 and the individual wolf
population down to 20.
Let’s Write!
What other switches and sliders can be adjusted to help out the sheep
population? Why?
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To help the sheep population you can increase individual-number-sheep and slide that all the way up
and or you can increase the sheep's reproduction to help the population of the sheep.
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DO THE FOLLOWING:
➔ Set initial-number-sheep to 80 and initial-number-wolves to 50 (this is close to how they were
when you first opened the model).
➔ Set sheep-reproduce to 10.0%.
➔ Click the setup
button.
➔ Click the go
button.
➔ Let the model run for about 100 time ticks
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
Let’s Write!
What happened to the wolves in this run? Why?
A lot of the wove during this run of 100 ticks were dying more than the sheep were dying. I think this
happens because the sheep reproduce double the time faster than the wolves reproduce.
When you open a model, all the sliders and switches are on a default setting. If you open a new model or
exit the program, your changed settings will not be saved.
In addition to sliders and switches, some models have choosers and input boxes. The Wolf Sheep
Predation doesn't have any of these.
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Step 5: Gathering Information With Plots And Monitors
The view lets you see what's going on in a model. NetLogo also provides has other ways of giving you
information about model run, such as plots and monitors.
Plots
The plot in Wolf Sheep Predation model contains three lines: sheep, wolves, and grass / 4. (The grass
count is divided by four so it doesn't make the plot too tall.) The lines show what's happening in the model
over time. The plot legend shows what each line indicates. In this case, it's the population counts.
When a plot gets close to becoming filled up, the horizontal axis is compressed and all of the data from
before gets squeezed into a smaller space. In this way, more room is made for the plot to grow.
If you want to save the plot, you can download it as an image. The installed version of NetLogo supports
exporting data as a CSV file with values of all monitors per time tick; unfortunately, NetLogo Web does
not support this.
Monitors
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Monitors are another means of displaying information from a model. Here are the monitors in Wolf Sheep
Predation model:
The monitors show us the population of sheep and wolves, and the amount of grass. (Remember, the
amount of grass is divided by four to keep the plot from getting too tall.)
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The numbers displayed in the monitors change as the model runs, whereas the plots show you data from
the whole course of the model run.
In the run of the simulation with the default values, the sheep population was lower in numbers then the
wolf population. We then adjusted the initial number of sheep and wolves favoring the sheep population
and still ended up with more wolves than sheep. Keeping the same values from the previous run, we then
increased the reproductive rate of the sheep, with the result of all sheep and no wolves. At what settings
would you find a balance between the three populations: grass, sheep and wolf? A balance means that all
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
three populations are in a relatively steady state without growing, or shrinking dramatically and without
apparent threat of extinction.
Let’s Paste!
with a
Place a screenshot in the box below showing the settings and the plots
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balance of grass, sheep, and wolf populations.
The NetLogo world is a two dimensional grid of patches. Patches are the individual squares in the grid. In
Wolf Sheep Predation, when the grass? switch is on the individual patches are easily seen, because
some are green, others brown.
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Think of the patches as being like square tiles in a room with a tile floor. By default, exactly in the middle
of the room is a tile labeled (0,0); meaning that if the room was divided in half one way and then the other
way, these two dividing lines would intersect on this tile. We now have a coordinate system that will help
us locate objects within the room:
Let’s Write!
How many
How many tiles away is the (0,0) tile from the right side of the room?
tiles away is the (0,0) tile from the left side of the room?
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
The number of tiles from the left side of the room is 3 tiles. The number of tiles on the right side of the
room was 3 tiles away.
In NetLogo, the number of tiles from right to left is called world-width. And the number of tiles from top to
bottom is world-height. These numbers are defined by top, bottom, left and right boundaries.
Step 6: Simulations Are Programmed
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At the bottom of the NetLogo Web web page there is a button to expand and show the NetLogo Code.
This is the code in the NetLogo programming language that makes the simulation happen. A programmer
took the behavior of wolves and sheep and their dependence on their environment (grass) and wrote
NetLogo code to make the elements in the simulation behave that way. Once you learn the NetLogo
language, you can edit the code and adapt the simulation to do new things, add more the environment,
etc. Or, you can think of your own things that you want to simulate and write the NetLogo code for it
yourself!
DO THE FOLLOWING:
➔ Click on the NetLogo Code tab at the bottom of the screen.
➔ Find where it says to go on a line by itself.
This is the code that is run when you click the go
Place a screenshot in the box below showing the code for to go.
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Let’s Paste!
button.
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
Unit One: Lesson 2 - Modeling And Simulation Activity Guide
Step 7: Other Models
Once you are done exploring the Wolf Sheep Predation model, you may want to take some time just to
explore some of the other models available in the Models Library in the drop down at the top of the
NetLogo Web web page.
DO THE FOLLOWING:
➔ Go through the model library and pick a model that is not the Wolf and Sheep Predation or the
Party simulation.
➔ Open it.
➔ Read the Model Info tab at the bottom of the screen.
In a few sentences explain what the model simulates and what you
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Let’s Write!
might do with it.
I think the sunflower simulation is The spirals found in the seeds, petals and branches of many plants
occur naturally through the growth of the flower.
Place a screenshot in the box below showing the model running for 100
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Let’s Paste!
ticks.
This tutorial was adapted from the NetLogo Tutorial 1: Models by Northwestern University.
This study source
was downloaded by 100000796630873 from CourseHero.com on 10-13-2021 17:05:27 GMT -05:00
https://www.coursehero.com/file/46671523/Lesson-2-Wolf-and-Sheep-Modeling/
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