symbolic matrix in matlab

[wave85]

Hi every body. I want to generate a 20*20 symbolic matrix in MATLAB. I am wondering how I could do that. I searched the net, and I found this command : A=sym('A',[20 20])
but whenever I typed this command in my MATLAB program, it sends error to me. Is anybody to help me?

Thanks a lot

 

[v_c]

Take a look at the explanations and the examples (toward the bottom of the page) here
Define symbolic objects - MATLAB

 

[wave85]

Thank u so much
I think my MATLAB software has a problem with sym syntax!!
I type :
A = sym('A%d%d', [3 4])

but I have following error:

??? Error using ==> sym.sym>char2sym at 408
Not a valid symbolic expression.

Error in ==> sym.sym at 92
S = char2sym(x);

 

[v_c]

Maybe you don't have the symbolic toolbox -- I don't think this is a standard part of the matlab distribution.
There is an additional cost to this toolbox. If you are looking for symbolic mathematical tools, there are free
options out there. One of them is Maxima Maxima, a Computer Algebra System
Check it out ... it does a lot of things very well and it is free!

 

[wave85]

Yeah, you are right. Thank u

 

[agreatstar]

It can easily be done y using loop.

Code:
function a=fu()

for i=1:20
for j=1:20
a(i,j)=sym(strcat('a',num2str(i),num2str(j)));
end
end
end