Information diffusion process model

extensions [ nw ]

turtles-own [ state ] ;; Three states of agents: "B" (believer) ;  "F" (factChecker) ; "S" (susceptible)

links-own [ weigth ]  ;; the weight of the links between agents

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;   SETUP   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

to setup
  ca
  setup-var
  setup-turtles
  update-plot
  reset-ticks
end 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;   GO   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

to go
  tick
  if ticks > 300 [stop]   ;; stop condition (300 units of time)

  spreading               ;
  forgetting              ;-- Three main procedures for agent's behavior
  veryfing                ;

  update-colors           ;; just to improve the visualisation
  update-plot             ;; update plots of the Interface
end 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  SETUP PROCEDURES  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

to setup-var
  set-default-shape turtles "person"
  set-default-shape links "curved link"
  update-output
end 

to update-output
  clear-output
  output-print "* Diffusion model in social networks *"
  if Type-of-network = "BA" [output-print "Barabási–Albert network"]
  if Type-of-network = "ER" [output-print "Erdős–Rényi network"]
end 

to setup-turtles
  if Type-of-network = "Barabási–Albert algorithm" [ nw:generate-preferential-attachment turtles links number-of-agents 3 ]
  if Type-of-network = "Erdős–Rényi model" [
    if number-of-agents > 100 [
      if PC-low-performance? and ask-proceed? [
        clear-output output-print (word "Erdős–Rényi model with " number-of-agents " nodes.")
        nw:generate-random turtles links number-of-agents 0.00585
      ]
    ]
  ]
 init-edges
end 

to init-edges
  ask links [set color 3]
  ask turtles
  [ setxy random-xcor random-ycor
    ifelse random 100 <= 90 [ set state "S" ][ set state "B" ]
  ]
  update-colors
end 

to update-colors
  ask turtles [
    if state = "B" [ set color blue ]
    if state = "F" [ set color red ]
    if state = "S" [ set color gray ]
  ]
end 

to update-plot
  set-current-plot "State-of-people"
  set-current-plot-pen "BELIEVERS"
  plot count turtles with [state = "B"]
  set-current-plot-pen "FACT-CHECKERS"
  plot count turtles with [state = "F"]
  set-current-plot-pen "SUSCEPTIBLES"
  plot count turtles with [state = "S"]
end 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  GO PROCEDURES ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

to spreading  ;; each agent modifies with some probability its state considering the points of view (states) of its neighbors;
  ; S -> B and S -> F according to:
  ; S -> B : "spreading" function for the hoax (fi)
  ; S -> F : disseminate among the immediate neighborhood of a vertex (gi)
  ask turtles with [state = "S"][
    let nB count link-neighbors with [state = "B"] ; n-of neighbors Believers
    let nF count link-neighbors with [state = "F"] ; n-of neighbors Fact-checkers
    let _1PlusA ( 1 + alpha-hoaxCredibility)
    let _1MinusA ( 1 - alpha-hoaxCredibility)
    let den (nB * _1PlusA + nF * _1MinusA)
    let f 0
    let g 0
    if den != 0 [
      set f beta-spreadingRate * ( nB * _1PlusA / den )
      set g beta-spreadingRate * ( nF * _1MinusA / den )
    ]

    let random-val-f random-float 1
    ifelse random-val-f < f
    [ set state "B" ]
    [ if random-val-f < (f + g) [ set state "F" ]
    ]
  ]
end 

to forgetting  ;; B -> S; F -> S  -- Each agent, regardless of belief state, forgets the news with a fixed probability pforget
  ask turtles with [state = "B" or state = "F"][
    if random-float 1 < pForget [
      set state "S"
    ]
  ]
end 

to veryfing  ;; B-> F ; each agent can fact-check the hoax with a fixed probability pverify;
  ask turtles with [state = "B"][
    if random-float 1 < pVerify [
      set state "F"
    ]
  ]
end 

;;;;;;;;;;;;;;;;;;;;;;; UTILS ;;;;;;;;;;;;;;;;;;;;;;;;;;;;

to-report ask-proceed?
  report user-yes-or-no? "The network can be too wide to display in old PC: may suggest you to disable 'view updates' before press 'GO' button? Press Y to continue"
end