matlab在循环之前分配上三角稀疏矩阵

Question

如何分配稀疏矩阵，其中上三角形部分为非零，下三角形部分为零？我目前正在查看spalloc（）函数

U = [0.046805;0.047415;0.048025;0.046805;0.047415;0.048025]; % small example here this can be very large!
V = [-0.000305;-0.000305;-0.000305;-0.000935;-0.000935;-0.000935]; % small example here this can be very large!
N = length(U);
A=zeros(N); % allocate upper triangular diagonal sparse matrix here
B=zeros(N); % allocate upper triangular diagonal sparse matrix here
for i=1:N-1
    for j=i+1:N
        A(i,j)=4*U(i)*U(j)/((U(i)+U(j)).^2+(V(i)-V(j)).^2);
        B(i,j) = sqrt((U(i)*U(j))/(A(i,j)));
    end
end
% Later do some maths with the non-zeros