lq_lu.m

lu 分解 b样条曲线

A=[2 2 3;4 7 7;2 -4 7];
b=[0 -3 6];
n=3;
x=zeros(3,1);
for i=1:n
    for j=1:i-1
        s=0;
        for k=1:j-1
            s=s+A(i,k)*A(k,j);
        end
        A(i,j)=(A(i,j)-s)/A(j,j);
    end
    for j=1:i
        s=0;
        for k=1:j-1
            s=s+A(j,k)*A(k,i);
        end
        A(j,i)=(A(j,i)-s);
    end
end
for i=1:n
    s=0;
    for k=1:i-1
        s=s+A(i,k)*b(k);
    end
    b(i)=b(i)-s;
end
for i=n:-1:1
    s=0;
    for k=i+1:n
        s=s+A(i,k)*x(k);
    end
    x(i)=(b(i)-s)/A(i,i);
end