sum_s1 = sum(M);
sum_s2 = sum(M, 2);
sum_st = sum(M(:));

nz = size(M,1);
ns = size(M,2);
nn = size(M(:),1);

sum_f1 = zeros(1,ns);
for kz = 1:nz
    sum_f1 = sum_f1 + M(kz,:);
end

sum_f2 = zeros(nz,1);
for ks = 1:ns
    sum_f2 = sum_f2 + M(:,ks);
end

sum_ft = 0;
for kn = 0:nn
    sum_ft = sum_ft + kn;
end