SensitiveDependence - a DRY version of the SensitiveDependence NetLogo script from complexityexplorer

SensitiveDependence.nlogo

turtles-own [xc xn]

to setup
  ;; (for this model to work with NetLogo's new plotting features,
  ;; __clear-all-and-reset-ticks should be replaced with clear-all at
  ;; the beginning of your setup procedure and reset-ticks at the end
  ;; of the procedure.)
  ;;__clear-all-and-reset-ticks
  clear-all
 
  draw-axes
  draw-parabola 
  
  ;; create the turtles in one go
  create-turtles 3 
  [
    set shape "dot"
    set size 5
    set xc x0
    set label-color black
  ]
 
 let x-list (list x0 x0' x0'')
 
 ;; initialize the turtles 
 (foreach [2 3 4] [0 1 2] [5 3 2] [blue red yellow]
 [ask turtle ?1
   [
     set xc item ?2 x-list
     set size ?3
     set color ?4
   ]])
 
 ;; do the first calculation
  ask turtles 
  [
    set xn (R * xc * (1 - xc))
    set xcor (xc * max-pxcor)
    set ycor (xn * max-pycor)
    set label (word precision xc 3 "," precision xn 3)
  ]
   reset-ticks
end

to go
  iterate  ; do one iteration of logistic map
;  update-plot
  wait .1
  tick  ; increase tick number by 1
end

to iterate
   ask turtles 
  [
    set xc xn
    set xn (R * xc * (1 - xc))
    set xcor (xc * max-pxcor)
    set ycor (xn * max-pycor)
    set label (word precision xc 3 "," precision xn 3)
  ]
  
end

to draw-axes   ; draws x and y axes
  ask patches 
    [set pcolor white]
  create-turtles 1
  ask turtles
  [
    set color black
    set xcor min-pxcor 
    set ycor min-pycor 
    set heading 0
    pen-down
    fd max-pycor   ; draw y axis
    pen-up
    set xcor min-pxcor 
    set ycor min-pycor
    set heading 90
    pen-down
    fd max-pxcor  ; draw x axis
    die
  ]
end

to draw-parabola  ; draws parabola representing logistic map for given value of R
 let x 0
 let y 0
 create-turtles 1 
  ask turtles 
  [
    set color black
    set xcor x * min-pxcor
    set ycor y * min-pycor
    pen-down
  ]
  repeat 10000
  [
    set x (x + .0001)
    ask turtles
    [
      set xcor (x * max-pxcor)
      set ycor (R * x * (1 - x)) * max-pycor
    ]
  ]
  ask turtles [die]
end
    
to-report x-current
  ifelse  turtle 2 != nobody [
    report [xc] of (turtle 2)
  ]
  [report x0
  ]
end

to-report x-new
  report [xn] of turtle 2
end
    

to-report x-current'
  ifelse turtle 3 != nobody [
    report [xc] of (turtle 4)
  ]
  [
    report x0'
  ]
end

to-report x-new'
  report [xn] of turtle 3
end

to-report x-current''
  ifelse turtle 4 != nobody [
    report [xc] of (turtle 4)
  ]
  [
    report x0''
  ]
end
;;plotting procedures -------------------

to setup-plot
  set-current-plot "logistic map"
  set-plot-x-range  0 1
  set-plot-y-range  0 1
end

to update-plot 
  set-current-plot-pen "x"
  plot x-current    
end