Van der Pol oscillator_01

globals [
  mylist-x
  mylist-y
  X
  Y
  dt
 ]

to setup

  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 ]
  ask patches with [ pxcor = 1 ] [  set pcolor white ]
  ask patches with [ pycor = 1 ] [  set pcolor white ]
  set mylist-x list 0 (X-slider)
  set mylist-y list 0 (Y-slider)
  system-dynamics-setup
  system-dynamics-do-plot
end 

to system-dynamics-setup
  reset-ticks
  set dt 0.001
  set X X-slider
  set Y Y-slider
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 phase-plot-color
    set xcor (last mylist-x * 40)
    set ycor (last mylist-y * 40)
    set size 0.7
    set shape "circle"
  ]
end 

to system-dynamics-go

  let local-m m
  let local-inflow inflow
  let local-inflow1 inflow1

  let new-X ( X + local-inflow1 )
  let new-Y ( Y + local-inflow )
  set X new-X
  set Y new-Y

  tick-advance dt
end 

to-report inflow
  report ( m * ( 1 - X * X ) * Y - X
  ) * dt
end 

to-report inflow1
  report ( m * Y
  ) * dt
end 

to system-dynamics-do-plot
  if plot-pen-exists? "X" [
    set-current-plot-pen "X"
    plotxy ticks X
  ]

  if plot-pen-exists? "Y" [
    set-current-plot-pen "Y"
    plotxy ticks Y
  ]
end 

to-report result-x
  report X
end 

to-report result-y
    report Y
end 

to clear-picture
  ca
end