suffragium.pairwise — suffragium 0.0.3

condorcet clj multimethod

Returns the condorcet winner if one exists from either a seq of ballots or the result of a pairwise election. In the former case a pairwise election is performed. Returns nil if there is no condorcet winner.

copeland clj multimethod

Perform a Copeland method election. Returns an array map of candidate keys and score values ordered from greatest to smallest score. The score of a candidate is its number of pairwise victories minus its number of pairwise defeats.

invert clj

(invert pg)

Takes the result of a pairwise election and reverses the direction of every edge. Useful if you want to find e.g. the condorcet loser.

llull-copeland clj multimethod

Perform a Copeland method election as originally proposed by Llull. Returns an array map of candidate keys and score values ordered from greatest to smallest score. The score of a candidate is its number of pairwise victories.

pairwise clj

(pairwise ballots)

Perform a pairwise election. Returns a loom weighted digraph. A pairwise election between two candidates is represented as a directed edge from the winner to the loser with a weight of the margin of victory. In the case of an edge to and from both candidates is created with a weight of 0.

Each ballot should contain a key for each candidate with an integer, lower value = more preferred. Candidates may be ranked as equally preferable.

ranked-pairs clj multimethod

Perform an election using Tideman's ranked pairs method. Returns an array map of candidate keys and score values, ordered from greatest to smallest score. The score of a candidate is its Copeland score on the graph of locked-in candidate pairs.

Accepts two optional arguments:

:tbrc is a tie-breaking order of the candidates, used to construct a tie-breaking ranking of the pairs. Used when pairs have the same margin. Must be a vector containing all candidates from most-preferred to least preferred. The default order should be considered an implementation detail.

:tbrp specifies the method used to construct a TBRP from the TBRC. Should be one of :zavist, :cretney, :legrand, :schulze-i, or :schulze-ii. Alternatively can be a vector containing all pairs of candidates as sub-vectors (in which case :tbrc is ignored). Defaults to :schulze-ii.

schulze clj multimethod

Perform an election using the Schulze method method. Returns a sequence of candidates from highest to lowest ranking. Uses margins to measure the strength of links.

Accepts two optional arguments:

:tbrc is a tie-breaking order of the candidates, used to construct a tie-breaking ranking of the pairs. Used when pairs have the same strength beatpath. Must be a vector containing all candidates from most-preferred to least preferred. If not specified the TBRC is the order of candidates returned by sort.

:tbrp specifies the method used to construct a TBRP from the TBRC. Should be one of :zavist, :cretney, :legrand, :schulze-i, or :schulze-ii. Alternatively can be a vector containing all pairs of candidates as sub-vectors (in which case :tbrc is ignored). Defaults to :schulze-ii.

schwartz-components clj

(schwartz-components pg)

Takes the results of a pairwise election and returns the Schwartz set components in no particular order.

schwartz-set clj

(schwartz-set pg)

Takes the results of a pairwise election and returns the Schwartz set.

smith-set clj

(smith-set pg)

Takes the results of a pairwise election and returns the Smith set.

weak-condorcet clj multimethod

Returns the weak condorcet winners if any exist from either a seq of ballots or the result of a pairwise election. In the former case a pairwise election is performed. Returns #{} if there are no weak condorcet winners.