Question

How do I create a matrix consisting of symbol elements in MATLAB R2009b?

The tedious way of doing this would be:

syms a11 a12 a21 a22
A = [a11 a12; a21 a22]

But if I want a 10×10 matrix I need something better.

Here I found the following command:

A = sym('A%d', [2 2]);

But it seems to only work in more recent versions of MATLAB while I’m using R2009b.

Answer 1

A not-so-efficient way of doing it would be to write a script to create a string and execute it with eval.

cmd_var = 'syms';
cmd_mat = 'A=[';
for i = 1:3
    for j = 1:3
        var = sprintf(' a_%d_%d ',i,j);
        cmd_var = [cmd_var var];
        cmd_mat = [cmd_mat var];
    end
    cmd_mat = [cmd_mat ';'];
end
cmd_var = [cmd_var ';'];
cmd_mat = [cmd_mat '];'];

So, the command strings look like this:

cmd_var =
syms a_1_1  a_1_2  a_1_3  a_2_1  a_2_2  a_2_3  a_3_1  a_3_2  a_3_3 ;

cmd_mat =
A=[ a_1_1  a_1_2  a_1_3 ; a_2_1  a_2_2  a_2_3 ; a_3_1  a_3_2  a_3_3 ;];

Now execute the command strings:

eval(cmd_var)
eval(cmd_mat)