Nodal admittance matrix using for loop and if statement

I want to ask how can I get the matrix Y if I have the value of y1, y12, y13, y23,...,etc.

I have coding as below, but it dose not work. Who can help me?

B_matrix =[0 2.5000 0 1.6667 5.0000 0; -2.5000 0 5.0000 2.5000 0 0;0 -5.0000 0 0 5.0000 0; -1.6667 -2.5000 0 0 0 0; -5.0000 0 -5.0000 0 0 0; 0 0 0 0 0 0]

Y=zeros(6,6);

for m=1:6

    for n=1:6  

        if m==n  

            for (k=1:6) & (k ~ = m)  

            Y(m,n)=B_matrix(m,n)+B_matrix(m,k);   

            else 

                Y(m,n)=-B_matrix(m,n); 

        end            
        end
        end  
end

Y

Answer 1

[Andrei Bobrov]

Y = diag(sum(B_matrix,2)) - (~eye(size(B_matrix))).*B_matrix;

[yu yue]

hi, it seems not right. Y(2,1)=-2.5; Y(2,2)=10; Y(3,2)=-5; Y(3,3)=10; Y(4,1) =-1.67, Y(4,2)= -2.5; Y(4,4)=4.17; Y(5,1)=-5; Y(5,3)=-5; Y(5,5)=10;

[Andrei Bobrov]

aB = abs(B_matrix);
Y = diag(sum(aB,2)) - (~eye(size(B_matrix))).*aB;