confmat.m

The pattern recognition matlab toolbox

%CONFMAT Construct confusion matrix
% 
%  [C,NE,LABLIST] = CONFMAT(LAB1,LAB2,METHOD,FID)
%
% INPUT
%  LAB1        Set of labels
%  LAB2        Set of labels
%  METHOD      'count' (default) to count number of co-occurences in
%	             LAB1 and LAB2, 'disagreement' to count relative
%		           non-co-occurrence.
%  FID         Write text result to file
%
% OUTPUT
%  C           Confusion matrix
%  NE          Total number of errors
%  LABLIST     Unique labels in LAB1 and LAB2
%
% DESCRIPTION
% Constructs a confusion matrix C between two sets of labels LAB1 
% (corresponding to the rows in C) and LAB2 (the columns in C). The order of 
% the rows and columns is returned in LABLIST. NE is the total number of 
% errors (sum of non-diagonal elements in C).
%
% When METHOD = 'count' (default), co-occurences in LAB1 and LAB2 are counted 
% and returned in C. When METHOD = 'disagreement', the relative disagreement 
% is returned in NE, and is split over all combinations of labels in C
% (such that the rows sum to 1). (The total disagreement for a class equals
% one minus the sensitivity for that class as computed by TESTC).
%
%   [C,NE,LABLIST] = CONFMAT(D,METHOD)
%
% If D is a classification result D = A*W, the labels LAB1 and LAB2 are 
% internally retrieved by CONFMAT before computing the confusion matrix.
%
% When no output argument is specified, or when FID is given, the
% confusion matrix is displayed or written a to a text file.
%
% EXAMPLE
% Typical use of CONFMAT is the comparison of true and and estimated labels
% of a testset A by application to a trained classifier W: 
% LAB1 = GETLABELS(A); LAB2 = A*W*LABELD.
% More examples can be found in PREX_CONFMAT, PREX_MATCHLAB.
% 
% SEE ALSO
% MAPPINGS, DATASETS, GETLABELS, LABELD

% Copyright: R.P.W. Duin, [e-mail]
% Faculty EWI, Delft University of Technology
% P.O. Box 5031, 2600 GA Delft, The Netherlands

% $Id: confmat.m,v 1.5 2007/11/09 10:50:32 duin Exp $

function [CC,ne,lablist1,lablist2] = confmat (arg1,arg2,arg3,fid)

	prtrace(mfilename);

	% Check arguments.
  if nargin < 4, fid = 1; end
	if nargin < 3 | isempty(arg3)
		if isdataset(arg1)
			lab1 = getlabels(arg1); lab2 = arg1*labeld;
			if nargin < 2| isempty(arg2)
				method = 'count';
				prwarning(4,'no method supplied, assuming count');
			else
				method = arg2;
			end
		else
			method = 'count';
			prwarning(4,'no method supplied, assuming count');
			lab1 = arg1;
			if (nargin < 2 | isempty(arg2))
				error('Second label list not supplied')
			end
			lab2 = arg2;
		end
	else
		lab1 = arg1;
		lab2 = arg2;
		method = arg3;
	end
	if nargin < 2
		if ~isdataset(arg1)
			error('two labellists or one dataset should be supplied')
		end
	end
		
	% Renumber LAB1 and LAB2 and find number of unique labels.

	m = size(lab1,1);
	if (m~=size(lab2,1))
		error('LAB1 and LAB2 have to have the same lengths.');
	end
	[nlab1,lablist1] = renumlab(lab1);
	[nlab2,lablist2] = renumlab(lab2);
	%[nlab1,nlab2,lablist] = renumlab(lab1,lab2);
	n1 = max(nlab1);
	n2 = max(nlab2);
	n = max(n1,n2); 
	
	% Construct matrix of co-occurences (confusion matrix).

	C = zeros(n1+1,n2+1);
	for i = 0:n1
		K = find(nlab1==i);
		if (isempty(K))
			C(i+1,:) = zeros(1,n2+1);
		else
			for j = 0:n2
				C(i+1,j+1) = length(find(nlab2(K)==j));
			end
		end
	end

	% position rejects and unlabeled object at the end of the matrix
	
	D = C;
	D(1:end-1,1:end-1) = C(2:end,2:end);
	D(end,:) = C(1,:);
	D(1:end-1,end) = C(2:end,1);
	C = D;
	D = D(1:end-1,1:end-1);
	DD = D(1:min(n1,n2),1:min(n1,n2));
	
	% Calculate number of errors ('count') or disagreement ('disagreement').
	% Neglect rejects

	switch (method)
		case 'count'								
			ne = sum(sum(D)) - sum(diag(DD));       % Diagonal entries are correctly
                                                % classified, so all off-diagonal
                                                % entries denote wrong ones.
		case 'disagreement'
			ne = (sum(sum(D)) - sum(diag(DD)))/m;   % Relative sum of off-diagonal 
                                             % entries.
			E = repmat(sum(D,2),1,n2);              % Disagreement = 1 - 
			D = ones(n1,n2)-D./E;                    % relative co-occurence.
			D = D / (n-1);
		otherwise
			error('unknown method');
	end
	
	%Distinguish 'rejects / no_labels' from 'non_rejects / fully labeled'
	
	if (any(C(:,end) ~= 0) | any(C(end,:)~=0)) & strcmp(method,'count')
		n1 = n1+1; n2 = n2+1;
		labch = char(strlab(lablist2),'reject');
		labcv = char(strlab(lablist1),'No');
	else
		labch = strlab(lablist2);
		labcv = strlab(lablist1);
		%labcv = labch;
		C = D;
	end

    % If no output argument is specified, pretty-print C.

	if (nargout == 0) | nargin == 4

		if nargin < 4, fid = 1; end
		
		% Make sure labels are stored in LABC as matrix of characters, 
    % max. 6 per label.

		if (size(labch,2) > 6)
			labch = labch(:,1:6); 
			%labcv = labcv(:,1:6); 
		end
		if (size(labch,2) < 5)
			labch = [labch repmat(' ',n2,ceil((5-size(labch,2))/2))]; 
			labcv = [labcv repmat(' ',n1,ceil((5-size(labcv,2))/2))]; 
		end

		nspace = max(size(labcv,2)-7,0);
		cspace = repmat(' ',1,nspace);
		%fprintf(fid,['\n' cspace '        | Estimated Labels']);
		fprintf(fid,['\n  True   ' cspace '| Estimated Labels']);
		fprintf(fid,['\n  Labels ' cspace '|']);
		for j = 1:n2, fprintf(fid,'%7s',labch(j,:)); end
		fprintf(fid,'|');
		fprintf(fid,' Totals');
		fprintf(fid,'\n ');
		fprintf(fid,repmat('-',1,8+nspace));
		fprintf(fid,'|%s',repmat('-',1,7*n2));
		fprintf(fid,'|-------');
		fprintf(fid,'\n ');
	
		for j = 1:n1
			fprintf(fid,' %-7s|',labcv(j,:));
			switch (method)
				case 'count'
					fprintf(fid,'%5i  ',C(j,:)');
					fprintf(fid,'|');
					fprintf(fid,'%5i',sum(C(j,:)));
				case 'disagreement'
					fprintf(fid,' %5.3f ',C(j,:)');
					fprintf(fid,'|');
					fprintf(fid,' %5.3f ',sum(C(j,:)));
			end
			fprintf(fid,'\n ');
		end

		fprintf(fid,repmat('-',1,8+nspace));
		fprintf(fid,'|%s',repmat('-',1,7*n2));
		fprintf(fid,'|-------');
		fprintf(fid,['\n  Totals ' cspace '|']);

		switch (method)
			case 'count'
				fprintf(fid,'%5i  ',sum(C));
				fprintf(fid,'|');
				fprintf(fid,'%5i',sum(C(:)));
			case 'disagreement'
				fprintf(fid,' %5.3f ',sum(C));
				fprintf(fid,'|');
				fprintf(fid,' %5.3f ',sum(C(:)));
		end
		fprintf(fid,'\n\n');
	end
	
	if nargout > 0
		CC = C;
	end

return