How to directly create a non-random upper or lower triangle matrix without creating a full square matrix?

I want to create the upper triangle matrix only directly in matlab and reflect it to make a full square matrix. I will assign numerical values to all the variables listed in the matrix.

Answer 1

[Rishabh Mishra]

Hi,

Consider the upper triangular matrix created below:

A = [1 2 3 4; 0 5 6 7; 0 0 8 9; 0 0 0 10]; 

To create the mirror image of upper triangle into the lower triangle, use the code below:

for i = 1:size(A,1) 
    for j = 1:size(A,1) 
        if j < i 
            A(i,j) = A(j,i); 
        end 
    end
end

Hope This helps.

[Raghu Echempati]

Thanks. But I do not want to type in zeros for A. If I create a null (6,6) or zeros(6) matrix, how do I just add the upper triangle coeffients to the null matrix? That makes it easy for me not to type the zeros to define matrix A. Thanks.

E.

[Raghu Echempati]

I hope you understood my question. How can I just create the elements (cofficients) of an upper or lower triangle matrix without adding zeros to make it a squre matrix?