MATLAB: Matlab Busy since four hours

busy

Here is my code which when run makes the matlab show busy since hours. What can be wrong? My data is big though!
Y = importdata('Dr_Kucukvar_data.xlsx');
linverse = importdata('L_inverse.txt');
X= Y.data.Diagonal;
mlinverse_1 = X(:,1);
mlinverse_1 = diag(mlinverse_1);
mlinverse_2 = X(:,2);
mlinverse_2 = diag(mlinverse_2);
mlinverse_3 = X(:,3);
mlinverse_3 = diag(mlinverse_3);
mlinverse_4 = X(:,4);
mlinverse_4 = diag(mlinverse_4);
mlinverse = [mlinverse_1 mlinverse_2 mlinverse_3 mlinverse_4];
Result_matrix = zeros(7824,1);
for i= 1:4
    u= 7824*(i-1)+1;
    g= u +7823;
    for j= 0:26
        for k= 96:107
            h= 163*j + k;
            z= zeros(7824,1);
            z(h)= 1;
            S = mlinverse(:,u:g) * linverse * z;
            Result_matrix = [Result_matrix S];
        end
    end
end

Best Answer

Your method of appending columns to 'Result_matrix' is very time consuming. Also as Geoff points out, your creation of a new 'z' matrix each time in the inner loop is very inefficient. I suggest you alter your code as follows:
   ......
   Result_matrix = zeros(7824,1297); % 1297 = 4*27*12+1
   c = 1;
   for i= 1:4
     u= 7824*(i-1)+1;
     g= u +7823;
     for j= 0:26
       for k= 96:107
         h= 163*j + k;
         S = mlinverse(:,u:g) * linverse(:,h);
         c = c+1;
         Result_matrix(:,c) = S;
       end
     end
   end
This should give you the same result and be considerably faster.
Final note: Do you really want the first column of Result_matrix to be all zeros?
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