Size of The Matrix in Diagonal Addition

Hello, I have to perform diagnoal matrix addition for one of my projects. The code is running successfully but the problem is that the resulting matrix is bing made of a bigger size than I need it to be.

here is my code :

% Development of an algorithim to add matrices diagnoally with 6 elements
% in common(under development )

% Size of S can be changed, but it should not be less than 12x12

S(1).model_data = sparse( rand( 13, 13 )) ;
S(2).model_data =  sparse( rand( 13, 13 )) ;
S(3).model_data = sparse( rand( 13, 13 )) ;

% Size of C is fixed, it cannot be changed
C = sparse( rand( 12, 12 )) ;

s = size(S(1).model_data,1); % size of matrix in a struct 
n = size(S,2);% number of matrices in the struct

b = (s+(s-1)+(n-2)*(s-1))+(size(C,2) -1);  %PROBLEM HERE % size of resulting matrix(T)

T = zeros(b,b); % resulting matrix
counter = 0; 
aa = 2;
for k = 1:1:(n+1)
    if (k == 2)
        y = size(C,2);
    else
        y = s ;
    end
    for i = 1:1:y % row 
        for j = 1:1:y % column
            if (k> aa)
                m = (size(C,2)-s) + ((k-1)*(s-6)); %after the C matrix
            else
                m =(k-1)*(s-6); % before the C matrix 
            end
        
            if (k == aa)
                
                T(i+m,j+m)= T(i+m,j+m) +C(i,j);
                counter = 1;
            else
            T(i+m,j+m)= T(i+m,j+m) +(S(k-counter).model_data(i,j));
            end
        end
    end
end

The highlighted variable b is giving me problems, does nay body knows how to fix it ?

[Walter Roberson]

You have not defined in the comments how the overlap is to take place, where C is to be placed relative to the S, and where the S are to be placed, and what the overlap scheme is.

Answer 1

[Walter Roberson]

b = n*s - 6*n + 12

The 12 is the constant size of C. The 6 is the overlap.

[Chris Dan]

Great!! Thanks for the answer :) :)