function Df = Dfiltre(u,D)

[pk,pkI] = max(D);

grndR = pkI;
pos = 1;
while pos
    grndR = grndR + 1;
    pos = (D(grndR) > 0);
end
grndR = grndR-1;
grndL = 2*pkI - grndR;

Df = vertcat(zeros(grndL-1,1),D(grndL:grndR),zeros(length(D)-grndR,1));