could i get help with this question?

can someone help me with this?

[Walter Roberson]

Please read http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[Steven Lord]

This sounds like a homework assignment. If it is, show us the code you've written to try to solve the problem and ask a specific question about where you're having difficulty and we may be able to provide some guidance.

If you aren't sure where to start because you're not familiar with how to write MATLAB code, I suggest you start with the free MATLAB Onramp tutorial to quickly learn the essentials of MATLAB.

If you aren't sure where to start because you're not familiar with the mathematics you'll need to solve the problem, I recommend asking your professor and/or teaching assistant for help.

[poppy]

FIRST Function for Gauss elimination:

function [x, A, b] = GE(A, b)
%-------------------------------------------------------------------------%
%GaussE: Function which performs Gauss Elimination, pivoting if required.
%INPUTS
% A = Input A matrix
% b = Input b vector

%OUTPUTS
% A   = The forward eliminated coefficient matrix
% b   = The forward eliminated b vector 
% x   = The final solution vector x 
%-------------------------------------------------------------------------%    
n = length(A); 
%-------------------------------------------------------------------------%
% FORWARD ELIMINATION START: 
%-------------------------------------------------------------------------%
for i = 1:(n-1)     % Pivot row index (stop at 2nd last row)
    %-------------------------------------------------------------------------%
    % < INSERT PARTIAL PIVOTING CODE HERE > 
    %-------------------------------------------------------------------------%
    for k = (i+1):n                             % Skips the pivot element and indexes what is BELOW it in the SAME COLUMN as the pivot element.
        factor = ( A(k,i) / A(i,i) );           % Calculates the row factor for current row
        for j = 1:n                             % Column index
            A(k,j) = A(k,j) - factor*A(i,j);    % Row subtraction, element-by-element
        end
        b(k) = b(k) - factor*b(i);              % Updates b   
    end
end
%-------------------------------------------------------------------------%
% FORWARD ELIMINATION END
%-------------------------------------------------------------------------%
%-------------------------------------------------------------------------%
% BACKWARDS SUBSTITUTION START: 
%-------------------------------------------------------------------------%
x = zeros(n,1);
x(n) = b(n) / A(n,n);                % Compute x(n) immediately 
for i = (n-1):(-1):(1)               % Row index, starting at the 2nd last row and working backwards
    summ = b(i);
    for j = (i+1):n                  % Before solving for x(i), need to subtract all terms to the RIGHT of the current pivot element (if any). 
        summ = summ - A(i,j)*x(j);   
    end
    x(i) = summ/A(i,i);             % Divide final 'sum' by the pivot element
    x
end
%-------------------------------------------------------------------------%
% BACKWARDS SUBSTITUTION END
%-------------------------------------------------------------------------%
end

Second function:

function [x]=BlockDiagonalSolver(A,b)
n=length(A); 
d=sqrt(length(A));
x=zeros(n,1); 
for i= 1:d 
    start_row=((i-1)*d+1);     
    end_row=(i*d);     
    h=start_row:end_row; 
    
    A_solve=A(h,h);     
    b_solve=b(h); 
    
    [A_1,b_1,x(h)]= GaussE(A_solve,b_solve);  
end

QUESTION: How would I go about generating a d block diagonal system for d = [ 5,10,15....50] and solve each system by integrating the two functions above.

[Walter Roberson]

See diag and blkdiag

Nothing in the assignment calls for integration.