2.4_BunniesLogisticModel.nlogo

breed [bunnies bunny]
globals [last-count]

Bunnies-own [old]

to setup
  ca
  let one-patch (patch-set patch 0 0)
  ask one-patch [sprout-bunnies initial-population [set old false set shape "bunny2" set color white set size 4 disperse]]
end

to reproduce
  if (count bunnies) > 0
  [
    ask bunnies [ set old true ]
    set last-count count bunnies
    ask one-of bunnies [ hatch-bunnies how-many-to-hatch  [ disperse ] ]  ;Ok, Not too realistic to have one bunny do all the reproductive work ... but easier to code.
    ask bunnies with [old] [die]
    do-plotting
  ]
end

to-report how-many-to-hatch
  let pop (count bunnies)
  let new-pop (birthrate - deathrate) * (pop  - ((pop * pop) / carrying-capacity))
  report round new-pop
end

to disperse
  set size size * .98 set heading random 360
  let new-x random max-pxcor
  let new-y random max-pycor
  let x-sign random 2
  let y-sign random 2
  ifelse (x-sign = 0) [set  xcor 0 - new-x] [set xcor new-x]
  ifelse (y-sign = 0) [set ycor 0 - new-y] [set ycor new-y]
  set old false
end

to do-plotting
  set-current-plot "Population vs. Time"
  plot count bunnies

  set-current-plot "This year's pop. vs. last year's pop."
  plotxy last-count count bunnies

end
@#$#@#$#@
GRAPHICS-WINDOW
235
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510
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ticks
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TEXTBOX
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10
158
32
Logistic Model
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95.0
1

BUTTON
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206
Reproduce
reproduce
NIL
1
T
OBSERVER
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BUTTON
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79
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Setup
setup\n
NIL
1
T
OBSERVER
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MONITOR
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147
436
NIL
count bunnies
17
1
11

PLOT
735
12
1094
173
Population vs. Time
Time
Population
0.0
10.0
0.0
10.0
true
false
"" ""
PENS
"" 1.0 0 -16777216 true "" "plot count turtles"

SLIDER
14
256
186
289
birthrate
birthrate
0
5.0
2.5
0.1
1
NIL
HORIZONTAL

PLOT
737
181
1096
341
This year's pop. vs. last year's pop.
Last year's pop.
This year's pop. 
0.0
10.0
0.0
10.0
true
false
"" ""
PENS
"pen-0" 1.0 0 -7500403 true "" "plotxy last-count count bunnies"

SLIDER
14
344
188
377
carrying-capacity
carrying-capacity
0
100
50.0
1
1
NIL
HORIZONTAL

SLIDER
14
215
186
248
initial-population
initial-population
0
20
20.0
1
1
NIL
HORIZONTAL

TEXTBOX
6
45
376
105
n      = (birthrate - deathrate) * (n  - (n    / k)),\n\nwhere k is the carrying capacity.
10
0.0
1

TEXTBOX
13
50
34
68
t+1
8
0.0
1

TEXTBOX
173
52
188
70
t
8
0.0
1

TEXTBOX
199
51
214
69
t
8
0.0
1

TEXTBOX
197
42
212
60
2
8
0.0
1

SLIDER
13
298
186
331
deathrate
deathrate
0
5.0
0.0
0.1
1
NIL
HORIZONTAL

@#$#@#$#@
## WHAT IS IT?

This model illustrates population growth using the logistic model.

## HOW IT WORKS

The model counts the number of rabbits at the end of each generation and then produces the correct number the following generation. To keep the math simple, there is no over-lapping of generations–that is, all the rabbits from one year replace themselves with offspring (according to the growth rate seting) and then perish.


## HOW TO USE IT

To use the model, press “setup” and then “reproduce”. Each time you press “reproduce” a generation of rabbits will be born.

## CREDITS AND REFERENCES

This model is part of the Dynamics series of the Complexity Explorer project.

Main Author:  John Balwit

Contributions from: Melanie Mitchell

Netlogo:  Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.


## HOW TO CITE

If you use this model, please cite it as: "Logistic Population Growth" model, Complexity Explorer project, http://complexityexplorer.org

## COPYRIGHT AND LICENSE

Copyright 2013 Santa Fe Institute.

This model is licensed by the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License ( http://creativecommons.org/licenses/by-nc-nd/3.0/ ). This states that you may copy, distribute, and transmit the work under the condition that you give attribution to ComplexityExplorer.org, and your use is for non-commercial purposes.
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pentagon
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person
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@#$#@#$#@
NetLogo 6.3.0
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