gini index

turtles-own [money
save_rate]

to setup
  clear-all
  reset-ticks
  create-turtles num_agents[
    set money (total_money / num_agents)
    setxy random-xcor random-ycor
    set save_rate random-float 1
  ]
end 

to go
  ask turtles[
    let agsets (other turtles-here)
    if count agsets >= 1[
      transaction(one-of agsets)
    ]
    forward 1
  ]
  tick
end 

to transaction[trader]
  let deltam 0
  let money0 ((1 - save_rate) * money)
  let money1 ((1 - save_rate) * [money] of trader)
  let epsilon (random-float 1)
  set deltam (epsilon - 1) * money0 + epsilon * money1

  if money + deltam >= 0 and money1 - deltam >= 0
  [
    set money money + deltam
    ask trader[
      set money money1 - deltam]
  ]
end 

to to-update-plot
let lst [money] of turtles
set-histogram-num-bars 100
if not empty? lst[
set-plot-x-range 0 max lst
histogram lst
]
end 

to save-file
  file-open "agents.txt"
  let wealths ""
  ask turtles[
    set wealths (word wealths money "\r\n")
  ]
  file-print wealths
  file-close
end 

to update-lorenz-plot
  clear-plot
  set-current-plot-pen "equal"
  plotxy 0 0
  plotxy 1 1

  set-current-plot-pen "dominant"
  plot-pen-down
  plotxy 0 0
  plotxy 1 0
  plotxy 1 1
  plot-pen-up

  set-current-plot-pen "lorenz"
  set-plot-pen-interval (1 / num_agents)
  plot 0

  let sorted-wealths sort [money] of turtles
  let total-wealth sum sorted-wealths
  let wealth-sum-so-far 0
  let index 0
  let gini 0
  let s 0

  repeat num_agents[
    set wealth-sum-so-far (wealth-sum-so-far + item index sorted-wealths)
    plot (wealth-sum-so-far / total-wealth)
    set index index + 1
    set s ((index / num_agents) - (wealth-sum-so-far / total-wealth)) / num_agents
    set gini gini + s
  ]

  set-current-plot "gini"
  plot gini * 2
end 

to-report compute-gini
    let sorted-wealths sort [money] of turtles
  let total-wealth sum sorted-wealths
  let wealth-sum-so-far 0
  let index 0
  let gini 0
  let s 0

  repeat num_agents[
    set wealth-sum-so-far (wealth-sum-so-far + item index sorted-wealths)
    plot (wealth-sum-so-far / total-wealth)
    set index index + 1
    set s ((index / num_agents) - (wealth-sum-so-far / total-wealth)) / num_agents
    set gini gini + s
  ]

  set-current-plot "gini"
  report gini * 2
end