function khi2_cal=calcul_khi2(tab_theo,tab_cont)
[nl,nc]=size(tab_theo);
khi2_cal=0;

for i=1:nl
   for j=1:nc
   khi2_cal=khi2_cal+(tab_cont(i,j)-tab_theo(i,j))^2/tab_theo(i,j);
end

end