RismanPreferentialAttachment

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Alexander Risman (Author)

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directed-link-breed [friendships friendship]

breed [persons person]
persons-own [
  in-friends
  out-friends
  total-friends
  extended-network
  ]

to setup
  clear-all
  create-persons number-of-people
   ask persons [
     move-to one-of patches
     set shape "person"
     set color red
      ]
end 

to go
  ifelse link-type = "directed"
  [go-directed]
  [go-undirected]
end 

to go-directed
  ask persons[
  
  set out-friends count out-friendship-neighbors
  set in-friends count in-friendship-neighbors
  let total-friend-set (turtle-set in-friendship-neighbors out-friendship-neighbors)
  set total-friends count total-friend-set
  let extended-network-set (turtle-set [in-friendship-neighbors] of total-friend-set 
    [out-friendship-neighbors] of total-friend-set total-friend-set)
  set extended-network count extended-network-set
  wiggle
    make-friends
    maintain-max
    
  ]
end  

to wiggle 
  rt random-float 360 fd 1
end 

to make-friends
  let prospect one-of other persons-here
  if prospect != nobody
  [
    if out-friends < max-out-friends
  [create-friendship-to prospect]
  if out-friends = max-out-friends
  [let worst-friend min-one-of out-friendship-neighbors [total-friends]
    if worst-friend != nobody
    [
  if [total-friends] of prospect > [total-friends] of worst-friend
  [ask out-friendship-to worst-friend [die] 
    create-friendship-to prospect]]
  ]
  ]
end 

to maintain-max
  let worst-out-friend min-one-of out-friendship-neighbors [total-friends]
  let worst-in-friend min-one-of in-friendship-neighbors [total-friends]
  if worst-out-friend != nobody
  [
    if out-friends > max-out-friends
  [ask out-friendship-to worst-out-friend [die] ]
  ]
  if worst-in-friend != nobody  
    [if in-friends > max-in-friends
    [ask in-friendship-from worst-in-friend [die] ]
    ]
end 

to cut-doubles
  ask turtles [ask out-friendship-neighbors
  [
    if out-friendship-neighbor? myself
    [ask in-friendship-from myself [die]
    ]
  ]]
end 

to go-undirected
  ask persons[
  let total-friend-set link-neighbors
  set total-friends count total-friend-set
  let extended-network-set (turtle-set [link-neighbors] of link-neighbors 
    total-friend-set)
  set extended-network count extended-network-set
  
  wiggle
  make-friends-undirected
  maintain-max-undirected
  ]
end 

to make-friends-undirected
  let prospect one-of other persons-here
  if prospect != nobody
  [
    if total-friends < max-total-friends
  [create-link-with prospect]
  if total-friends = max-total-friends
  [let worst-friend min-one-of link-neighbors [total-friends]
    if worst-friend != nobody
    [
  if [total-friends] of prospect > [total-friends] of worst-friend
  [ask link-with worst-friend [die] 
    create-link-with prospect]]
  ]
  ]
end 

to maintain-max-undirected
  let worst-friend min-one-of link-neighbors [total-friends]
  if worst-friend != nobody
  [
    if total-friends > max-total-friends
  [ask link-with worst-friend [die] ]
  ]
end

There are 3 versions of this model.

Uploaded by	When	Description	Download
Alexander Risman	almost 13 years ago	No description provided	Download this version
Alexander Risman	almost 13 years ago	No description provided	Download this version
Alexander Risman	almost 13 years ago	Initial upload	Download this version

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