%CLEVALB Classifier evaluation (learning curve), bootstrap version
%
% E = CLEVALB(A,CLASSF,TRAINSIZES,NREPS)
%
% INPUT
% A Training dataset
% CLASSF Classifier to evaluate
% TRAINSIZES Vector of class sizes, used to generate subsets of A
% (default [2,3,5,7,10,15,20,30,50,70,100])
% NREPS Number of repetitions (default 1)
%
% OUTPUT
% E Error structure (see PLOTE)
%
% DESCRIPTION
% Generates at random, for all class sizes defined in TRAINSIZES, training
% sets out of the dataset A and uses these for training the untrained
% classifier CLASSF. CLASSF may also be a cell array of untrained
% classifiers; in this case the routine will be run for all of them. The
% resulting trained classifiers are tested on all objects in A. This
% procedure is then repeated N times.
%
% Training set generation is done "with replacement" and such that for each
% run the larger training sets include the smaller ones and that for all
% classifiers the same training sets are used.
%
% If CLASSF is fully deterministic, this function uses the RAND random
% generator and thereby reproduces if its seed is reset (see RAND).
% If CLASSF uses RANDN, its seed may have to be set as well.
%
% Use FID = 1 to report progress to the command window.
%
% EXAMPLES
% See PREX_CLEVAL.
%
% SEE ALSO (<a href="http://37steps.com/prtools">PRTools Guide</a>)
% MAPPINGS, DATASETS, CLEVALB, TESTC, PLOTE
% Copyright: R.P.W. Duin, duin@ph.tn.tudelft.nl
% Faculty of Applied Sciences, Delft University of Technology
% P.O. Box 5046, 2600 GA Delft, The Netherlands
% $Id: clevalb.m,v 1.4 2008/07/03 09:05:50 duin Exp $
function e = clevalb(a,classf,learnsizes,nreps,fid)
% use of fid is outdated
if (nargin < 4) || isempty(nreps)
prwarning(2,'number of repetitions not specified, assuming NREPS = 1');
nreps = 1;
end;
if (nargin < 3) || isempty(learnsizes)
prwarning(2,'vector of training set class sizes not specified, assuming [2,3,5,7,10,15,20,30,50,70,100]');
learnsizes = [2,3,5,7,10,15,20,30,50,70,100];
end;
% If a single mapping is given, convert it to a 1 x 1 cell array.
if (ismapping(classf)), classf = {classf}; end
% Correct for old argument order.
if (isdataset(classf)) & (ismapping(a))
tmp = a; a = classf; classf = {tmp};
end
if (isdataset(classf)) & (iscell(a)) & (ismapping(a{1}))
tmp = a; a = classf; classf = tmp;
end
if ~iscell(classf), classf = {classf}; end
% Assert that all is right.
isdataset(a); ismapping(classf{1});
% Remove requested class sizes that are larger than the size of the
% smallest class.
mc = classsizes(a); [m,k,c] = getsize(a);
toolarge = find(learnsizes >= min(mc));
if (~isempty(toolarge))
prwarning(2,['training set class sizes ' num2str(learnsizes(toolarge)) ...
' larger than the minimal class size in A; removed them']);
learnsizes(toolarge) = [];
end
learnsizes = learnsizes(:)';
% Fill the error structure.
nw = length(classf(:));
datname = getname(a);
e.n = nreps;
e.error = zeros(nw,length(learnsizes));
e.std = zeros(nw,length(learnsizes));
e.xvalues = learnsizes(:)';
e.names = [];
e.xlabel = 'Training set size';
if (nreps > 1)
e.ylabel= ['Averaged error (' num2str(nreps) ' experiments)'];
elseif (nreps == 1)
e.ylabel = 'Error';
else
error('Number of repetitions NREPS should be >= 1.');
end;
if (~isempty(datname))
e.title = ['Bootstrapped learning curve on ' datname];
end
if (learnsizes(end)/learnsizes(1) > 20)
e.plot = 'semilogx'; % If range too large, use a log-plot for X.
end
% Report progress.
s1 = sprintf('clevalb: %i classifiers: ',nw);
prwaitbar(nw,s1);
% Store the seed, to reset the random generator later for different
% classifiers.
seed = randreset;
% Loop over all classifiers (with index WI).
for wi = 1:nw
isuntrained(classf{wi});
name = getname(classf{wi});
e.names = char(e.names,name);
prwaitbar(nw,wi,[s1 name]);
% E1 will contain the error estimates.
e1 = zeros(nreps,length(learnsizes));
% Take care that classifiers use same training set.
randreset(seed); seed2 = seed;
% For NREPS repetitions...
s2 = sprintf('cleval: %i repetitions: ',nreps);
prwaitbar(nreps,s2);
for i = 1:nreps
prwaitbar(nreps,i,[s2 int2str(i)]);
% Store the randomly permuted indices of samples of class CI to use in
% this training set in JR(CI,:).
JR = zeros(c,max(learnsizes));
for ci = 1:c
JC = findnlab(a,ci);
% Necessary for reproducable training sets: set the seed and store
% it after generation, so that next time we will use the previous one.
randreset(seed2);
R = ceil(rand(1,max(learnsizes))*length(JC));
JR(ci,:) = JC(R)';
seed2 = randreset;
end
li = 0; % Index of training set.
nlearns = length(learnsizes);
s3 = sprintf('cleval: %i sizes: ',nlearns);
prwaitbar(nreps,s3);
for j = 1:nlearns
nj = learnsizes(j);
prwaitbar(nlearns,j,[s3 int2str(j) ' (' int2str(nj) ')']);
li = li + 1;
% J will contain the indices for this training set.
J = [];
for ci = 1:c
J = [J;JR(ci,1:nj)'];
end;
% Train classifier CLASSF{WI} on this training set and calculate
% error.
W = a(J,:)*classf{wi};
e1(i,li) = testc(a,W);
end
prwaitbar(0);
end
prwaitbar(0);
% Calculate average error and standard deviation for this classifier
% (or set the latter to zero if there's been just 1 repetition).
e.error(wi,:) = mean(e1,1);
if (nreps == 1)
e.std(wi,:) = zeros(1,size(e.std,2));
else
e.std(wi,:) = std(e1)/sqrt(nreps);
end
end
prwaitbar(0);
% The first element is the empty string [], remove it.
e.names(1,:) = [];
return