% Evaluate performance of unsupervised POS tagging algorithm
% Many-to-1, 1-to-1, NVI metrics.

% If you use this code, please cite:
%   Michael Lamar*, Yariv Maron*, Mark Johnson, Elie Bienenstock. 
%   SVD and clustering for unsupervised POS tagging. (ACL 2010) 
% For more information, see the above reference.

function [MTO_score, OTO_score, NVI_score] = eval_labels( labels, tags )

%     MTO_score - Many-to-One score
%     OTO_score - One-to-One score
%     NVI_score - Normalized Variation of Information score

conf_matrix = sparse(tags, labels, 1);    % gold tags are rows, induced labels are columns
conf_matrix = full(conf_matrix/sum(conf_matrix(:)));

[MTO_score, MTO_tag] = max(conf_matrix);
MTO_score = sum(MTO_score);                         % many-to-one score
[OTO_score, OTO_tag] = one2one_map_all(conf_matrix);    % one-to-one
[H1, H2, VI] = var_information(conf_matrix);
NVI_score = VI/H1;                                  % Normalized VI

display(['Many-to-1: ' num2str(MTO_score) ...
    '  Greedy 1-to-1: ' num2str(OTO_score) ...
    '  NVI: ' num2str(NVI_score)]);