Lotka-Volterra Equation: Phase Plane
Model was written in NetLogo 6.0.1
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globals [ mylist-x mylist-y sheep-birth-rate predation-rate predator-efficiency wolf-death-rate sheep wolves dt ] to setup ;clear-all clear-globals clear-ticks clear-patches clear-all-plots ask patches with [ pxcor = 0 ] [ set pcolor white ] ask patches with [ pycor = 0 ] [ set pcolor white ] setup-coordinates set mylist-x list 0 (sheep) set mylist-y list 0 (wolves) system-dynamics-setup system-dynamics-do-plot end to system-dynamics-setup reset-ticks set dt 0.009 set sheep-birth-rate sheep-birth-rate-slider set predation-rate predation-rate-slider set predator-efficiency .8 set wolf-death-rate 0.15 set sheep sheep-num set wolves wolves-num end to clear-picture ca end to go system-dynamics-go system-dynamics-do-plot set mylist-x lput result-x mylist-x set mylist-y lput result-y mylist-y crt 1 [ set color select-phase-plot-color set xcor (last mylist-x * 0.15) set ycor (last mylist-y * 0.15) set size 0.5 set shape "circle" ] if ticks >= 300 [ stop ] end to system-dynamics-go let local-sheep-births sheep-births let local-sheep-deaths sheep-deaths let local-wolf-births wolf-births let local-wolf-deaths wolf-deaths let new-sheep max( list 0 ( sheep + local-sheep-births - local-sheep-deaths ) ) let new-wolves max( list 0 ( wolves + local-wolf-births - local-wolf-deaths ) ) set sheep new-sheep set wolves new-wolves tick-advance dt end to-report sheep-births report ( sheep-birth-rate * sheep ) * dt end to-report sheep-deaths report ( sheep * predation-rate * wolves ) * dt end to-report wolf-births report ( wolves * predator-efficiency * predation-rate * sheep ) * dt end to-report wolf-deaths report ( wolves * wolf-death-rate ) * dt end to-report result-x report sheep end to-report result-y report wolves end to setup-coordinates ask patch -5 5 [ set plabel "0" set plabel-color white ] ask patch -7 160 [ set plabel "1000" set plabel-color white ] ask patch -7 80 [ set plabel "500" set plabel-color white ] ask patch 160 -5 [ set plabel "1000" set plabel-color white ] ask patch 320 -5 [ set plabel "2000" set plabel-color white ] ask patch -5 -48 [ set plabel "-50" set plabel-color white ] ask patch -40 -5 [ set plabel "-50" set plabel-color white ] ask patch -10 193 [ set plabel "Wolves" set plabel-color blue ] ask patch 380 -10 [ set plabel "Sheep" set plabel-color red ] end to system-dynamics-do-plot if plot-pen-exists? "sheep" [ set-current-plot-pen "sheep" plotxy ticks sheep ] if plot-pen-exists? "wolves" [ set-current-plot-pen "wolves" plotxy ticks wolves ] end
There is only one version of this model, created about 7 years ago by Victor Iapascurta.
Attached files
File | Type | Description | Last updated | |
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Lotka-Volterra Equation: Phase Plane.png | preview | Preview for 'Lotka-Volterra Equation: Phase Plane' | about 7 years ago, by Victor Iapascurta | Download |
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Francesc Morales
Error opening the file
I have just downloaded the last version of NetLogo, and when I try to open the model it says: "Expected nlogo to have 12 sections, this had 10" What is going on? Thank you!
Posted almost 7 years ago
Victor Iapascurta
The error while opening the model
Since the model was built in NetLogo 6.0.1 this might be the problem and solution. Although the two version 6.0.1 and 6.0.2 are 'compatible' the problem may be because of the model building 'procedure': part of the model was created in SDM than converted to 'regular' Netlogo. You can download the 6.0.1 version and try to open the model with it. Regards, The author
Posted almost 7 years ago