Spatial Opinion Dynamics with Two Types of Mixing

extensions [rnd]

globals [
  fizz ; measures the frequency of attitudes that change at each step
  L2 ;frequency of -2 attitudes
  L1 ;frequency of -1 attitudes
  R1 ;frequency of 1 attitudes
  R2 ;frequency of 2 attitudes
  interface-density
  relocate-timer
  telephone-timer
  num-turtles
  last-cross ;this is the last time step where the centers cross (1 if they never did)
  last-op-cross ; this is the last time step where the opinions cross (1 if they never did)
  higher-center ; this keeps track of which center has the higher frequency
  higher-op
]

turtles-own [
  old-attitude
  new-attitude
]

to setup
  clear-all
  ask patches [set pcolor gray]
  set-default-shape turtles "square"
  make-turtle-distribution
  ask turtles [
    set size 1.2
    set old-attitude new-attitude
    set color 5 - ((old-attitude / max-entrench) * 4.9)
  ] ; in order to do synchronous updating, we need to delay when agents update their attitudes, so we separate attitudes into new and old
  set fizz 0
  measure-frequency-over-time
  set num-turtles count turtles
  ifelse L1 > R1 [set higher-center "L1"] [set higher-center "R1"]
  ifelse (L1 + L2) > (R1 + R2) [set higher-op "L"] [set higher-op "R"]
  set last-cross 1
  if measure-interface-density [measuring-interface-density]
  reset-ticks
end 

to go
  if not any? turtles with [old-attitude >= 1] or not any? turtles with [old-attitude <= -1] [stop]
  ask turtles [ local-interactions ]
  if relocation [ relocate ]
  if telephone? [
    ifelse telephone-timer = 0 [set telephone-timer telephone-freq] [set telephone-timer telephone-timer - 1 ]
  ]
  set fizz (count turtles with [old-attitude != new-attitude]) / count turtles
  ask turtles [
    set old-attitude new-attitude
    set color 5 - ((old-attitude / max-entrench) * 4.9)
  ]
  measure-frequency-over-time
  check-last-cross
  if measure-interface-density [measuring-interface-density]
  tick
end 

to local-interactions
  let j nobody ; j will be the other agent, which we initially set as nobody
  ifelse influence = "max-inf" or influence = "min-inf" [
    if influence = "max-inf" [
      set j max-one-of turtles-on neighbors [abs old-attitude] ]
    if influence = "min-inf" [
      set j min-one-of turtles-on neighbors [abs old-attitude] ]
  ]
  [
    ifelse telephone? and telephone-timer = 0 and random-float 1 < frac-to-telephone [
      set j one-of turtles
    ]
    [
      set j rnd:weighted-one-of (turtles-on neighbors) [abs influence-function [old-attitude] of self]
    ]
  ]
  if is-turtle? j [ ;it is possible that no agent ends up getting picked in the line above, so this checks that someone has
    ifelse random-float 1 < opinion-amplification [
      if [old-attitude] of j > 0 [
        if abs old-attitude < max-entrench [
          ifelse old-attitude = -1 [set new-attitude 1] [ set new-attitude old-attitude + 1 ]]
      ]
      if [old-attitude] of j < 0 [
        if abs old-attitude < max-entrench [
          ifelse old-attitude = 1 [set new-attitude -1] [set new-attitude old-attitude - 1 ]]
    ]]
    [
      if [old-attitude] of j > old-attitude [
        ifelse old-attitude = -1 [set new-attitude 1] [ set new-attitude old-attitude + 1]]
      if [old-attitude] of j < old-attitude [
        ifelse old-attitude = 1 [ set new-attitude -1][set new-attitude old-attitude - 1 ]]
    ]
  ]
end 

to relocate ; much faster then using "ask turtles []"
  let allagents [self] of n-of (floor (frac-to-relocate * num-turtles)) turtles ; create a list of all agents
  let total ((length allagents) - 1)
  let i 0
  while [i < total] ; for each 2 agents in a list
  [
    let tempx [xcor] of item i allagents
    let tempy [ycor] of item i allagents
    ask (item i allagents) [
      set xcor [xcor] of item (i + 1) allagents
      set ycor [ycor] of item (i + 1) allagents]
    ask (item (i + 1) allagents) [set xcor tempx set ycor tempy]
    set i (i + 2) ; increment index by 2
  ]
end 

to-report influence-function [item1]
  if influence = "linear" [
    ifelse item1 = 0 [report 1] [report item1] ]  ; this is the linear update function
  if influence = "square" [
    ifelse item1 = 0 [report 1] [report (item1 ^ 2)]] ; this weighs extreme attitudes more than moderate ones
  if influence = "uniform" [
    if item1 < 0 [report -1]
    if item1 > 0 [report 1] ]
  if influence = "co-linear" [
    ifelse item1 = 0 [report 1] [report (max-entrench + 1 - abs item1) ] ]
  if influence = "co-square" [
    ifelse item1 = 0 [report 1] [report (max-entrench + 1 - abs item1) ^ 2 ] ]
end 

to make-turtle-distribution
  ifelse rnd-initial [
    ask patches [;; every patch will either have a positive or negative attitude placed on them. The probability of one over the other is set by polluter-to-nonpolluter-ratio
      ifelse random-float 1 < positive-to-negative-ratio [
        sprout 1 [
          set new-attitude (random init-attitude) + 1
        ]
      ]
      [
        sprout 1 [
          set new-attitude 0 - (random init-attitude) - 1
        ]
      ]
    ]
  ][;;otherwise, the positive attitudes are arranged to form a circle, with a radius set by radius-size
    ask patches [
      ifelse (abs pxcor) ^ 2 + (abs pycor) ^ 2 <= radius-size ^ 2 [
        sprout 1 [
          set new-attitude max-entrench
        ]
      ]
      [
        sprout 1 [
          set new-attitude (0 - max-entrench)
        ]
      ]
    ]
  ]
end 

to check-last-cross
  let hc ""
  ifelse L1 > R1 [set hc "L1"] [set hc "R1"]
  if higher-center != hc [
    set higher-center hc
    set last-cross ticks
  ]
  let ho ""
  ifelse (L1 + L2) > (R1 + R2) [set ho "L"] [set ho "R"]
  if higher-op != ho [
    set higher-op ho
    set last-op-cross ticks
  ]
end 

to measuring-interface-density
  let g []
  ask turtles [
    let d 0
    ask turtles-on neighbors [
      if ([old-attitude] of self * [old-attitude] of myself) < 0 [set d d + 1]
    ]
  set g fput (d / 8) g
  ]
  set interface-density mean g
end 

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;; STATISTICS
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to measure-frequency-over-time
  set L2 count turtles with [old-attitude = -2] / count turtles
  set L1 count turtles with [old-attitude = -1] / count turtles
  set R1 count turtles with [old-attitude = 1] / count turtles
  set R2 count turtles with [old-attitude = 2] / count turtles
end 

;; Copyright Bert Baumgaertner
;; See info tab for credits