Patch Coordinates Example

breed [centers center]
breed [searchers searcher]

to setup
  clear-all
  ask patches [ set pcolor gray ]
  ask patch start-x start-y [ set pcolor green ]
  create-searchers 1
  [
    set heading 0
    set color red
    set size 0.2
    set shape "circle"
    setxy start-x start-y
  ]
  create-centers 1
  [
    set color blue
    set size 0.1
    set shape "circle"
    setxy start-x start-y
  ]
  reset-ticks
end 

to go
  ;; this is to reset the patches to gray so it changes
  ;; when you move the start-x or start-y slider
  ask patches [ set pcolor gray ]

  ;; this resets the center turtle to the point indicated by the sliders
  ask centers [ setxy start-x start-y ]

  ask searchers
  [
    setxy start-x start-y    ;; return to center
    set pcolor green
    rt 5                     ;; it goes clockwise in 5 degree increments
    fd distance-of-travel    ;; go back out to edge of circle
    set pcolor black
  ]
  tick
end 


; Public Domain:
; To the extent possible under law, Uri Wilensky has waived all
; copyright and related or neighboring rights to this model.