MATLAB: Updating element defined as a variable in a matrix for a given range

MATLABmatrix element

Hello,
I created a gauss elimination with partial pivoting and back substitution to solve a system of linear equations. What I am having trouble with is creating a matrix that has an element defined as a variable that is updated for a given range of numbers in order to produce a number of solutions based on the range and increments provided. I recieve the following error message:"Error using vertcat: Dimensions of arrays being concatenated are not consistent."
Thank you for your help.
function [x] = FwdElimPPivBckSub(A,b)
tic
R3 = (30.1:.1:100);
A = [1 -1 -1 0 0;
    0 0 1 -1 -1;
    30 0 0 -25 -25;
    -25 0 R3 0 -6;
    0 0 -6 0 21;];
b = [0; 0; 110; 0; -45];
n = length(b);
for k = 1:n-1
    p = k;
    big = abs(A(k,k));
    for ii = k+1:n
        dummy = abs(A(ii,k));
        if dummy > big
            p = ii;
        end
    end
    if p ~= k
        for jj = k:n
            dummy = A(p,jj);
            A(p,jj)= A(k,jj);
            A(k,jj)= dummy;
        end
        dummy = b(p);
        b(p) = b(k);
        b(k) = dummy;
    end
    for i = k+1:n
    factor = A(i,k)/A(k,k);
    for  j = k+1:n
        A(i,j) = A(i,j)-factor *A(k,j);
    end
    b(i) = b(i) - factor*b(k);
    end
end
for i = 1:n
x(i) = b(i)/A(i,i);
end
for i = n-1:-1:1
    sum = b(i);
    for j = i+1:n
        sum = sum - A(i,j)*x(j);
    end
    x(i) = sum/A(i,i);
end
toc

Best Answer

R3 = (30.1:.1:100);
R3 is now 1 x 700
A = [1 -1 -1 0 0;
    0 0 1 -1 -1;
    30 0 0 -25 -25;
first row, second row, third are all 1 x 5
    -25 0 R3 0 -6;
There is an R3 in the middle there, and it is 1 x 700, so this line is 1 x (2 + 700 + 2) which is 1 x 704
    0 0 -6 0 21;];
and that line is 1 x 5.
What I am having trouble with is creating a matrix that has an element defined as a variable that is updated for a given range of numbers in order to produce a number of solutions based on the range and increments provided.
You pass in A and b. You should not be defining them inside the function. You should be calling the function in a loop, passing in different variations of A, and doing something appropriate with the results returned by the function.
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