Social Influence

extensions[nw] 
globals[number-influence]

to setup
  clear-all
  nw:set-context turtles links
  set-default-shape turtles "circle"
  ask turtles[
  set color one-of [yellow green]
  set shape "circle"]
  make-node nobody     
  make-node turtle 0     
  reset-ticks
end 

to go
  ask links [ set color gray ]
  make-node find-partner
  tick
  if layout? [ layout ]
end 

to make-node [old-node]  
  crt 1
  [
    set color one-of [yellow green]  ;one-of [red blue]  ;set color [color] of old-node 
    if old-node != nobody [
      create-link-with old-node [set color blue]
      set color [color] of old-node 
    ]
      ;move-to old-node
      fd 8
      set number-influence number-influence + 1
]
end 

to-report find-partner
  report one-of turtles
end 
; report one-of turtles


;;;;;;;;;;;;;;
;;; Layout ;;;
;;;;;;;;;;;;;;

;; resize-nodes, change back and forth from size based on degree to a size of 1

to resize-nodes
  ifelse all? turtles [size <= 1]
  [
    ;; a node is a circle with diameter determined by
    ;; the SIZE variable; using SQRT makes the circle's
    ;; area proportional to its degree
    ask turtles [ set size sqrt count link-neighbors ]
  ]
  [
    ask turtles [ set size 1 ]
  ]
end 

to layout
  ;; the number 3 here is arbitrary; more repetitions slows down the
  ;; model, but too few gives poor layouts
  repeat 3 [
    ;; the more turtles we have to fit into the same amount of space,
    ;; the smaller the inputs to layout-spring we'll need to use
    let factor sqrt count turtles
    ;; numbers here are arbitrarily chosen for pleasing appearance
    layout-spring turtles links (1 / factor) (7 / factor) (1 / factor)
    display  ;; for smooth animation
  ]
  ;; don't bump the edges of the world
  let x-offset max [xcor] of turtles + min [xcor] of turtles
  let y-offset max [ycor] of turtles + min [ycor] of turtles
  ;; big jumps look funny, so only adjust a little each time
  set x-offset limit-magnitude x-offset 0.1
  set y-offset limit-magnitude y-offset 0.1
  ask turtles [ setxy (xcor - x-offset / 2) (ycor - y-offset / 2) ]
end 

to-report limit-magnitude [number limit]
  if number > limit [ report limit ]
  if number < (- limit) [ report (- limit) ]
  report number
end