function bivpdf (seta,wa,setb,wb,bmin,bmax)
% function bivpdf (seta,wa,setb,wb,bmin,bmax)
% Plot the bivariate PDF of two variables ('seta' and 'setb')
% by using two bin widths ('wa' and 'wb')

% Copyright (c) 2004-2006 Alessio Botta, Alberto Dainotti, Antonio Pescapè
% Email: {a.botta , alberto , pescape }@unina.it
% DIS - Dipartimento di Informatica e Sistemistica 
% University of Napoli Federico II, ITALY
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bins = (min(seta)+wa/2):wa:max(seta);
bbins = (min(setb)+wb/2):wb:max(setb);
n=length(bins);
m=length(setb);
if (bmin==0 && bmax==0)
    bmin=1;
    bmax=length(bins);
end
N=length(seta);
old_res=0;
for i=bmin:bmax
    data = zeros(length(seta),1);
    data(find(seta>=(bins(i)-wa/2) & seta<(bins(i)+wa/2)))=setb(find(seta>=(bins(i)-wa/2) & seta<(bins(i)+wa/2)));
    set=data(find(data));
    [z(:,(i-bmin+1)),x1] = hist(set,bbins);
    if (sum(z(:,(i-bmin+1))))
        %z(:,(i-bmin+1)) = z(:,(i-bmin+1)) / sum(z(:,(i-bmin+1)));
        z(:,(i-bmin+1)) = z(:,(i-bmin+1)) / N;
    end
    res=floor(((i-bmin+1)/(bmax-bmin+1)*100));
    if(res ~= old_res)
        old_res=res;
        st=mat2str(res);
        disp(strcat(st,'% completed'))
    end
end
[xxs yys]=meshgrid(bins(bmin:bmax),bbins);
surf(xxs,yys,z);