Disease simple

globals
[
  how-many-people
  percent-sick-to-start
]


turtles-own
[
  infected?           ;; If true, the person is infected
  cured?              ;; If true, the person has lived through an infection.
  susceptible?        ;; Tracks whether the person is susceptible
  recovery-time       ;; How long this turtle takes to recover
  has-been-infected?  ;; Tracks whether the person has even been infected
  infection-length    ;; How long the person has been infected
]


;;;
;;; SETUP PROCEDURES
;;;

to setup
  clear-all
  set how-many-people 300
  set percent-sick-to-start 10
  setup-people
  reset-ticks
end 

to setup-people
  let number-immune 0
  let number-infected ((how-many-people - number-immune) * (percent-sick-to-start / 100))
  let number-susceptible (how-many-people - number-immune - number-infected)

  ;; Create the vaccinated turtles
  create-turtles number-immune
  [
    setxy random-xcor random-ycor
    set cured? false
    set infected? false
    set susceptible? false
    set has-been-infected? false

    set shape "person"

    ;; Set the recovery time for each agent to fall on a
    ;; normal distribution around average recovery time
    set recovery-time random-normal average-recovery-time average-recovery-time / 4

    ;; make sure it lies between 0 and 2x average-recovery-time
    if recovery-time > average-recovery-time * 2 [
      set recovery-time average-recovery-time * 2
    ]
    if recovery-time < 0 [ set recovery-time 0 ]


    assign-color
  ]


  ;; Create the infected turtles
  create-turtles number-infected
  [
    setxy random-xcor random-ycor
    set cured? false
    set infected? true
    set susceptible? false
    set has-been-infected? true

    set shape "person"

    ;; Set the recovery time for each agent to fall on a
    ;; normal distribution around average recovery time
    set recovery-time random-normal average-recovery-time average-recovery-time / 4

    ;; make sure it lies between 0 and 2x average-recovery-time
    if recovery-time > average-recovery-time * 2 [
      set recovery-time average-recovery-time * 2
    ]
    if recovery-time < 0 [ set recovery-time 0 ]


    assign-color
  ]

  ;; Create the susceptible turtles
  create-turtles number-susceptible
  [
    setxy random-xcor random-ycor
    set cured? false
    set infected? false
    set susceptible? true
    set has-been-infected? false

    set shape "person"

    ;; Set the recovery time for each agent to fall on a
    ;; normal distribution around average recovery time
    set recovery-time random-normal average-recovery-time average-recovery-time / 4

    ;; make sure it lies between 0 and 2x average-recovery-time
    if recovery-time > average-recovery-time * 2 [
      set recovery-time average-recovery-time * 2
    ]
    if recovery-time < 0 [ set recovery-time 0 ]


    assign-color
  ]
end 

;; Different people are displayed in 3 different colors depending on health
;; White is a healthy but susceptible person
;; Green is a healthy immune (non-susceptible) person
;; Red is an infected person

to assign-color  ;; turtle procedure
  (ifelse
    infected?
    [
      set color red
    ]
    susceptible?
    [
      set color white
    ]
    [
      set color blue  ;; immune
    ])
end 


;;;
;;; GO PROCEDURES
;;;

to go
  if all? turtles [ not infected? ]
    [ stop ]

  ask turtles
    [ move ]

  ask turtles with [ infected? ]
    [ infect
      maybe-recover ]

  ask turtles
    [ assign-color ]

  tick
end 


;; People move about at random.

to move  ;; turtle procedure
  rt random-float 360
  fd 1
end 


;; Infection can occur to any susceptible person nearby

to infect  ;; turtle procedure
   let nearby-susceptible (turtles-on neighbors)
     with [ susceptible? ]

     if nearby-susceptible != nobody
     [ ask nearby-susceptible
       [ if random-float 100 < infection-chance
         [
           set infected? true
           set susceptible? false
           set has-been-infected? true
         ]
       ]
     ]
end 

to maybe-recover
  set infection-length infection-length + 1

  if infection-length > recovery-time
  [
    set infected? false
    set cured? true
    ifelse immune-after-recovery
       [ set susceptible? false ]
       [ set susceptible? true ]

  ]
end 


; Copyright 2011 Uri Wilensky.
; See Info tab for full copyright and license.