v2.0.0

This update will break some of the backwards compatibility, so we have incremented the major version number.

Added

• A PreferenceInterval class.
• MCMC sampling for both BradleyTerry ballot generators.
• Add print statement to BallotGraph so that when you draw the graph without labels, it prints a dictionary of candidate labels for you.
• Add an IRV election class, which is just a wrapper for STV with 1 seat.
• Add default option to Borda election class, so users do not have to input a score vector if they want to use the traditional Borda vector.
• Add several methods to PairwiseComparisonGraph. Added two boolean methods that return True if there is a condorcet winner or if there is a condorcet cycle. Added two get methods that return the winner or the cycles. Cached the results of dominating_tiers and get_condorcet_cycles.
• Added optional to_float method to first_place_votes if users want to see them as floats instead of Fractions.
  -Added a by_bloc parameter to generate_profile. If True, this returns a tuple, the first entry of which is a dictionary of PreferenceProfiles by bloc. The second entry is the aggregated profile. This is very helpful for analyzing the behavior of a single bloc of voters. Defaults to False for backwards compatibility.
• Created a Cumulative ballot generator class. The Cumulative class works like PL, but samples with replacement instead of without. The ranking order does not matter here, simply that candidates are listed on the ballot with multiplicity.
• Created a HighestScore election class. This takes in a profile and a score vector, and returns the candidates with highest scores. There is a lot of flexibility in the score vector, so this class can run things like Borda, cumulative, etc.
• Created a Cumulative election class which is just a subclass of HighestScore with the score vector set to all 1s. Thus anyone appearing on the ballot gets one point for each time they appear.
• Wrote an __add__ method for PreferenceProfile that combines the ballot lists of two profiles.
• Created utility functions to compute the winners of a profile given a score vector, as well as to validate a score vector (non-negative and non-increasing).
• Created a shortPlackettLuce class which allows you to generate ballots of arbitrary length in the style of PL.
• Added tests for __add__ method of PreferenceProfile.
• Added SlatePreference model and tests.

Changed

• Change the way the condense_ballots() method works in profiles. Rather than altering the original profile, it returns a new profile. This gives users the option to preserve the original profile.

• Alter STV class so that the remaining candidates are always listed in order of current first place votes.

• Made PlackettLuce a subclass of shortPlackettLuce.

• Change PlackettLuce, BradleyTerry, and Cumulative ballot generators to have name_ prefix. This is in contrast to the slate_ models we have introduced.

• Speed improvements for various ballot generators.

• pref_interval_by_bloc is now pref_intervals_by_bloc in all ballot generators. This is now a dictionary of dictionaries, where the both sets of keys are the blocs, and the values of the sub-dictionaries are PreferenceInterval objects. The slate models require that we sample from the uncombined PreferenceInterval objects, while the name models require that we combine the PreferenceInterval objects using cohesion parameters.

• MDS plot functionality, splitting it into compute_MDS which computes the coordinates, and plot_MDS which plots them. Made because the computation is the most time intensive.

Fixed

• Fixed an error in the PreferenceProfile tail method.
• Errors in bloc labeling in CambridgeSampler.

Deprecations

• Deprecated PL and BT to name_PL and name_BT

Full Changelog: v1.1.1...v2.0.0