MATLAB: Problem with equationsToMatrix function and symbolic matrix

equationstomatrix

My code obtains temperature distribution of a 2d plate. There is a for loop for 2 equations (one for heated side and one for interior points). I first create a symbolic matrix of temperature distribution. And problem starts here. Since i need every point as symbols, I used this:

T = sym('T',[n,n],'positive');

There is no problem with this notation up to 10×10 system. However, for 11 and above, when i use equationsToMatrix, first elements of the A matrix are dislocated. I think this is because the elements are named as T1_1, T1_2… and T11_1 comes before T1_1 or something like that. I am not really sure but the problem comes from naming elements. I don't know how to create a large symbolic matrices such as 10×10, 11×11, 15×15 without using this naming. But i need to fix the problem for matrices larger than 10×10. Can anyone give me an idea to fix it?

Best Answer

T = sym(compose('T%02d_%02d', (1:n).', 1:n))

Related Solutions

MATLAB: How to make a mtrix of N symbolic variables dependant on ‘t’

I found solution, don't remember where, but hope it would be useful for others.

N1 = 5;
N2 = 5;
syms t
for k1 = 0 : N1
    for k2 = 0 : N2
        PSI_t = ['PSI_f_' num2str(k1 + 1) '_' num2str(k2 + 1) '(t_ent1)'];
        PSI(k1 + 1, k2 + 1) = symfun(PSI_t, t);
    end
end

First, we need to make a name of the symbolic function which we can address and which includes the matrix indexes. After that we make it being a function of other variables as an element of another matrix.

Now we can address the symbolic functions as PSI(1, 2) and use it in equations. As for the initial conditions or other stuff, we can use subs:

example_condition = subs(PSI(1, 1), t, 0) == 1;

MATLAB: “Undefined function ‘equationsToMatrix’ for input arguments of type ‘sym’.” Error

I think this is related to couple of issues combined. MATLAB was on E:\ drive, I'd uninstalled and installed it again on C:\.

I've made toolbox path cache update afterwards. Now it is working.

P.S.: After posting this question, I realized that most of the symbolic functions gone crazy. This problem is not directly related to equationsToMatrix function.

Thanks for the replies.

Ozgur

Best Answer

Related Solutions

MATLAB: How to make a mtrix of N symbolic variables dependant on ‘t’

MATLAB: “Undefined function ‘equationsToMatrix’ for input arguments of type ‘sym’.” Error

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