function [filesProc, errorC] = balanceDB(files, maxNumInd, maxNumSampleInd)

%init

errorC = 0;

filesProc = files;

%loop on files to compute num of samples for each ind

numSamplePerInd = zeros(numel(filesProc), 1); %larger init to be sure

for i = 1 : numel(filesProc) 

    filename = filesProc(i).name;

    %class

    [C, ~] = strsplit(filename, {'_', '.'});

    ind = str2double(C{2}) + 1;

    numSamplePerInd(ind) = numSamplePerInd(ind) + 1;  

end %for i

%remove excess

im = find(numSamplePerInd, 1, 'last');

numSamplePerInd(im+1 : end) = [];

%remove individual without minimum number of samples

indexrem = [];

for i = 1 : numel(filesProc)

    filename = filesProc(i).name;

    %class

    [C, ~] = strsplit(filename, {'_', '.'});

    ind = str2double(C{2}) + 1;

    if numSamplePerInd(ind) < maxNumSampleInd

        indexrem = [indexrem i];

    end %if numSamplePerInd(ind) == 1

end %for i

filesProc(indexrem) = [];

%check if there are enough

if numel(filesProc) < maxNumInd

    errorC = -1;

    return;

end %if numel(filesProc) < maxNumInd

%remove excess individuals

indexrem = [];

allInd = [];

for i = 1 : numel(filesProc)

    filename = filesProc(i).name;

    %class

    [C, ~] = strsplit(filename, {'_', '.'});

    ind = str2double(C{2}) + 1;

    if numel(find(allInd == ind)) == 0

        allInd = [allInd ind];

    end %if numel

    if numel(allInd) > maxNumInd

        %we can remove the others

        allInd(end) = [];

        indexrem = i : numel(filesProc);

        break;

    end %if numInd > maxNumInd

end %for i

filesProc(indexrem) = [];

%discard samples in excess

indexrem = [];

numSamplePerInd = zeros(numel(filesProc), 1); %larger init to be sure

for i = 1 : numel(filesProc) 

    filename = filesProc(i).name;

    %class

    [C, ~] = strsplit(filename, {'_', '.'});

    ind = str2double(C{2}) + 1;

    numSamplePerInd(ind) = numSamplePerInd(ind) + 1; 

    if numSamplePerInd(ind) > maxNumSampleInd

        indexrem = [indexrem i];

    end %if numSamplePerInd(ind) > maxNumSampleInd

end %for i   

filesProc(indexrem) = [];