;; modified by eytan bakshy for version NetLogo 4.0

patches-own [r g b culturalFeatures Mycount player PlayerList Matches OpeningsList ListSize OpeningsIndex FeaturesIndex Trait]

to setup

  ;;clear the model
  ca
  
  ;;set the global clock to 0
  reset-ticks
  
  ;;issue a set of initialization commands to all patches in the model
  ask patches 
    [
     
    ;;creates a list object for storing traits
    set culturalFeatures []
    
    ;;initializes the list
    while [features > (length culturalFeatures)]
    [
      set culturalFeatures lput random(traits) culturalFeatures
    ]
    
    ;;calls the color method for initial show of model
    doColor
    ]
    display
end

;;Main Method of the model
to go
  ;;Issue a set of commands to all patches
  ask patches [match  doColor]
    
  ;;increment global clock
  tick
  
  ;;update graphs
;  do-plots
end

;;Each Patche executes the following procedure
to match
  ;;restset the variables used in this procedure
  set Mycount 0;
  set Matches 0;
  set OpeningsList []
  set ListSize -1
  set OpeningsIndex -1
  set FeaturesIndex -1
  set Trait -1
  
  ;;randomly select a neighbor to interact with 
  set player one-of neighbors

  ;;get the neighbor's list of traits
  set PlayerList [culturalFeatures] of player

  ;;compare my traits with my neighbor's traits
  foreach culturalFeatures
  [
    ifelse (item Mycount PlayerList = ?)
    [
      ;;record count of matches
      set Matches Matches + 1   
    ] 
    [
     ;; record the index of non-matches
      set OpeningsList lput Mycount OpeningsList  
    ]
    ;;keep track of how what index in the list we are at
    set Mycount Mycount + 1
  ]

  ;;turn the count of matches into a fraction
  set Matches (Matches / features)  
  
  ;;interact with probability equal to similarity
  if ((Matches > random-float 1.0) and (Matches < 1))
  [
      set ListSize length OpeningsList;; size of index list
      set OpeningsIndex random(ListSize);; random spot in index list
      set FeaturesIndex item OpeningsIndex OpeningsList ;; find index to use
      set Trait item FeaturesIndex PlayerList ;; use index to get Trait
      
      ;;copy a randomly selected trait to one of the non-matching traits
      set culturalFeatures replace-item FeaturesIndex culturalFeatures Trait
  ]
end

;;This uses the values of the traits to determine the coloring of the patches
to doColor
    set MyCount 0
    foreach culturalFeatures
    [
        if (MyCount = 0)
         [set r  ? / traits]
        if (MyCount = 1)
         [set g  ? / traits]
        if (MyCount = 2)
         [set b  ? / traits]
         set MyCount MyCount + 1
       ]
    set pcolor (list (255 * r) (255 * g) (255 * b))
  ;  set pcolor random 12
end





;;Put into Go

  ;;A global command that selects a single patch to execute
 ;; if (noise > random(1000))
 ;; [
 ;;   ask random-one-of patches [perturb]
 ;; ]


;;Randomly replaces a feature
to perturb
    set FeaturesIndex random(features)    
    show culturalFeatures
    set Trait random(traits)
    set culturalFeatures replace-item FeaturesIndex culturalFeatures Trait 
    show culturalFeatures
end


;to do-plots 
;  if not plot-groups? [ stop ]
;  set-current-plot "Patch Colors" 
;  set-current-plot-pen "color5" 
;  plot  count patches with [about-color 5 pcolor]
;  set-current-plot-pen "color15" 
;  plot  count patches with [about-color 15 pcolor]
;  set-current-plot-pen "color25" 
;  plot  count patches with [about-color 25 pcolor]
;  set-current-plot-pen "color35" 
;  plot  count patches with [about-color 35 pcolor]
;  set-current-plot-pen "color45" 
;  plot  count patches with [about-color 45 pcolor]
;  set-current-plot-pen "color55" 
;  plot  count patches with [about-color 55 pcolor]
;  set-current-plot-pen "color65" 
;  plot  count patches with [about-color 65 pcolor]
;  set-current-plot-pen "color125" 
;  plot  count patches with [about-color 125 pcolor]
;  set-current-plot-pen "color85" 
;  plot  count patches with [about-color 85 pcolor]
;  set-current-plot-pen "color95" 
;  plot  count patches with [about-color 95 pcolor]
;end 

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"color55" 1.0 0 -11352576 true
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@#$#@#$#@
WHAT IS IT?
-----------
If the process of local imitation is a dominant feature of cultural life, why is there so much cultural diversity in the world?  This model presents Robert Axelrod's answer to this paradox of cultural diffusion.  Each patch engages in a process of local imitation based on homophily (similarity of traits) with its neighbors.  While local neighborhoods converge to a set of traits, under some conditions the population diverges - creating multiple cultural groups.


HOW IT WORKS
------------
Each round a patch looks at its neighbors.  Selecting one neighbor at random, the patch evaluates how many traits it has in common with the neighbor.  With probability equal to the similarity between the active patch and its neighbor, the active patch selects a non-matching feature and changes its trait to match its neighbor's.  Thus, the more similar that two patches are, the more similar that they become.

HOW TO USE IT
-------------
The features slider describes the number of different cultural features that each agent has - the number of loci for interaction.  The traits slider is the number of values that an agent can have at each locus.  The model is initialized so that each feature is randomly set to a value between 1 and traits.    


THINGS TO TRY
-------------
Try to determine what settings drive the model to cultural heterogeneity vs. cultural homogeneity.  How do Traits, Features, and system size interact to affect the model?


EXTENDING THE MODEL
-------------------
Change the decision algorithm to eliminate probabilities of 0 and 1, making the system ergodic.
Add external perturbations (noise) to the model.
Add repulsion (xenophobia) to the model (so that patches become less like patches that are already dissimilar from them)


RELATED MODELS
--------------
Genetic Drift


CREDITS AND REFERENCES
----------------------
Contributed by Damon Centola
based on Robert Axelrod's "Dissemination of Culture", Journal of Conflict Resolution, 1997.
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