SIR Model - COVID19

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Paul Smaldino (Author)

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;;SIR Model with random movement
;;Agents move around at random.
;;They are either Susceptible, Infected, or Recovered (or, equivalently, removed)
;;
;;Coded in 2020 by Paul Smaldino
;;http://smaldino.com/wp/
;;
;;-----------------------------------------
;;CREATIVE COMMONS LICENSE
;;This code is distributed by Paul Smaldino under a Creative Commons License:
;;Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
;;https://creativecommons.org/licenses/by-sa/4.0/


globals [max-infected]

turtles-own[
  infected?
  immune?
]

to setup
  clear-all
  setup-turtles
  setup-infected
  set max-infected (count turtles with [infected?])
  reset-ticks
end 

to setup-turtles
  create-turtles num-turtles [
    set color white
    set shape "person"
    set size 2
    set infected? false
    set immune? false
    setxy random-pxcor random-pycor
  ]
end 

to setup-infected
  ask n-of init-infected turtles [
   set color red
   set infected? true
  ]
end 

to go
  ;;stop if everyone or noone is infected
  if (count turtles with [infected?] = 0)
  or (count turtles with [infected?] = num-turtles)
  [stop]

  infect-susceptibles
  recover-infected
  recolor
  move
  calculate-max-infected
  tick
end 

to infect-susceptibles ;; S -> I
  ask turtles [
    let infected-neighbors (count other turtles with [color = red] in-radius 1)
    if (random-float 1 <  1 - (((1 - transmissibility) ^ infected-neighbors)) and not immune?)
    [set infected? true]
  ]
end 

to recolor
  ask turtles with [infected?]
  [ set color red]
end 

to move
  ask turtles [
    right random 360 ;;get a new random heading
    forward speed
  ]
end 

to recover-infected ;;I -> R
  ask turtles with [infected?]
  [
    if random-float 1 < recovery-rate
    [
      set infected? false
      ifelse remove-recovered?
      [
        set immune? true
        set color gray
      ]
      [
        set color white
      ]
    ]
  ]
end 

to calculate-max-infected
  let x (count turtles with [infected?])
  if x > max-infected
  [set max-infected x]
end 

to-report max-infected-prop
  report max-infected / num-turtles
end 

to-report prop-uninfected
  report (count turtles with [not infected? and not immune?]) / num-turtles
end

There is only one version of this model, created over 5 years ago by Paul Smaldino.

Attached files

File	Type	Description	Last updated
SIR Model - COVID19.png	preview	Preview for 'SIR Model - COVID19'	over 5 years ago, by Paul Smaldino	Download

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