Opinion Dynamics: Friedkin-Johnsen Model - Basic

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Mutian Zhao (Author)

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globals [
  num-agents          ;; Number of agents
  neighbor-radius     ;; Radius for neighbor detection
  step-counter        ;; Time step counter
]

turtles-own [
  opinion             ;; Agent's opinion (0-1)
  self-weight         ;; Weight given to self-opinion
  neighbor-weights    ;; List associating neighbors with their weights
]

to setup
  clear-all
  reset-ticks

  ;; Parameter initialization
  set num-agents 200
  set neighbor-radius 5
  set step-counter 0

  ;; Create agents (uniform distribution)
  create-turtles num-agents [
    set shape "circle"
    set size 1.5

    ;; Random position and opinion
    setxy random-xcor random-ycor
    set opinion random-float 1  ;; Uniformly distributed initial opinions
    update-weights  ;; Initialize weights
    update-color    ;; Set color based on opinion
  ]
end 

to update-weights
  ;; Clear and recalculate all weights
  set self-weight 0.2  ;; Fixed self-weight at 0.2
  set neighbor-weights []  ;; Empty neighbor weights list

  ;; Get neighbor agents (excluding self)
  let my-neighbors other turtles in-radius neighbor-radius
  let neighbor-total-weight 0
  let neighbor-list sort my-neighbors

  ;; Calculate neighbor weights (excluding self)
  foreach neighbor-list [ n ->
    let dist distance n
    let w exp (-5 * dist)  ;; Weight calculated using exponential decay
    set neighbor-weights lput (list n w) neighbor-weights
    set neighbor-total-weight neighbor-total-weight + w
  ]

  ;; Normalize neighbor weights (sum of neighbor weights = 1)
  let normalized-neighbor-weights []
  foreach neighbor-weights [ pair ->
    let neighbor item 0 pair
    let weight item 1 pair
    set normalized-neighbor-weights lput (list neighbor (weight / neighbor-total-weight)) normalized-neighbor-weights
  ]

  set neighbor-weights normalized-neighbor-weights
end 

to update-color
  ;; More positive opinions (near 1) are lighter blue
  ;; More negative opinions (near 0) are darker blue
  set color scale-color blue opinion 0 1
end 

to go
  if not any? turtles [ stop ]

  ;; Update weights and calculate new opinions
  ask turtles [
    update-weights
    let new-op 0

    ;; Contribution from self-opinion
    set new-op new-op + self-weight * opinion

    ;; Weighted contributions from all neighbors
    let neighbor-influence 0
    foreach neighbor-weights [ pair ->
      let neighbor item 0 pair
      let weight item 1 pair
      set neighbor-influence neighbor-influence + weight * [opinion] of neighbor
    ]
    set new-op new-op + (1 - self-weight) * neighbor-influence

    set opinion new-op
    update-color  ;; Update color mapping
  ]

  set step-counter step-counter + 1
  tick
end

There are 2 versions of this model.

		Uploaded by	When	Description	Download
		Mutian Zhao	about 1 month ago	translate	Download this version
		Mutian Zhao	about 1 month ago	Initial upload	Download this version

Attached files

File	Type	Description	Last updated
GIF1.gif	gif	With agents having fixed social interaction ranges, group opinions fragment into several camps, giving rise to localized opinion assimilation.	about 1 month ago, by Mutian Zhao	Download
Opinion Dynamics: Friedkin-Johnsen Model - Basic.png	preview	Initially, attitudes are uniformly distributed. The lighter a turtle's color, the more positive its opinion; conversely, the darker the color, the more negative its opinion.	about 1 month ago, by Mutian Zhao	Download

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