;; text, like this, that start with semi-colons are comments and do not effect anything
;;
;; First we have lists of general and individual properties/slots

globals []

breed [parties party]
breed [voters voter]

;; 
parties-own [political-position votes won?]
voters-own [political-position]

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Next we have the procedure to initialise the simulation
;; this is executed when one presses the "setup" button

to setup 
  clear-all ;; this clears everything at the start - a clean slate

  ;; create the parties
  create-parties number-of-parties [
    ;; give them an initial random political position
    set political-position random-float 1
    update-party-appearence
  ]
  
  ;; create voters with random political positions
  create-voters number-of-voters [
    set political-position random-float 1
    update-voter-appearence
  ]
  
  reset-ticks                            ;; this initialises the simulation time system and graphs
end

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Next we have the procedure to progress the simulation one time step
;; this is executed when one presses the "step" button or repeatedly
;; if one presses the "go" button

to vote
  ;; chosen party is a variable needed later so declare it
  let chosen-party nobody
  ;; nob party has any votes at the start of an election and none has won
  ask parties [
    set votes 0
    set won? false
   ]
  
  ask voters [
    ;; each voter chooses the party that is nearest to it in terms of political position
    set chosen-party min-one-of 
                        parties 
                        [abs (political-position - [political-position] of myself)]
    ;; then increases that party's vote by one
    ask chosen-party [set votes votes + 1]

  ]
  
  ;; find the party with the most votes and set their state to having won
  ask max-one-of parties [votes] [set won? true]
  
  ask parties [
    ;; parties are displayed with a height proportional to their vote and an expression
    ;; happy or sad depending on wether they won or not
    update-party-appearence
  ]
  
  tick                                   ;; this progresses the simulation time by one
end

to shift
  ;; for parties that did not win...
  ask parties with [not won?]
    ;; shift their political position randomly, bounded by 0 and 1
    [ set political-position political-position + random-normal 0 0.01
      if political-position < 0 [set political-position 0]
      if political-position > 1 [set political-position 1]
      ;; redisplay them
      update-party-appearence
    ]
end

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Finally we have definitions of the various action words/commands we use in the above
;; this makes the code easier to read and so that chunks of code can be reused at will
;; DO NOT WORRY about the detail of these (yet)

to update-voter-appearence
  set xcor max-pxcor * political-position  ;; the position accross represents their political position
  set size 3
  set ycor min-pycor + size
end

to update-party-appearence
  set size 10 
  ;; how far up the world they are represents num of votes received
  set ycor min-pycor + 8 + (max-pycor - min-pycor - 8) * votes / number-of-voters 
  set xcor max-pxcor * political-position
end
@#$#@#$#@
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@#$#@#$#@
## WHAT IS IT?

This is an example model, used as part of the "2-day Introduction to Agent-Based Modelling".  

This illustrates the mutual adjustment self-organisation of agents and voting.  The actions of the agents affect the party's internal states (votes, won?) which subsequently affects its actions.

## HOW IT WORKS

All voters and parties have a position on the political spectrum from 0 to 1.  Voters vote for the party nearest to them in terms of this spectrum.  The parties with the most votes get elected.  Parties that do not get elected randomly shift their political position a bit.

## HOW TO USE IT

Press...

"setup" - initialises the simulation, placing voters and parties between 0 and 1
"vote" - causes an election, voters voting for the nearest party
"shift" - parties that are not elected randomly shift their position a bit
"vote+shift" - do "vote" then "shift"
"10x vote+shift" - do "vote+shift 10 times
"go" - repeatedly do vote+shift

## THINGS TO NOTICE

This is a self-organised critical system (ala Per Bak).  Eventually an unsuccessful party edges near enough to the successful's parties position that it get elected.

In a 3-party contest with 1 winner, the middle party is usually squeezed by the others and rarely does well.

If one wing is strongly contested by more parties, the other wing's party tends to win.

## THINGS TO TRY

1. Change the shape of the parties to "face happy" or "face sad" depending on whether they were elected (won?)
1. Change the colour of voters to match who they voted for
1. Add a graph to show the political position of the party with most votes
1. change the initial distribution of voters to a normally distributed one

## NETLOGO FEATURES

Note use of min-one-of (to find the party with the smallest political distance to a voter) and max-n-of (to find the top n parties that get elected).

## CREDITS AND REFERENCES

Model by Bruce Edmonds, Feb 2013
http://cfpm.org/simulationcourse
@#$#@#$#@
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