MATLAB: For loop with symbolic expressions

errorfor loopsymbolic

I am trying to make a for loop that put symbolic expressions inside a matrix ( in positions given by index of for loop) and i get this error:

    ??? The following error occurred converting from sym to double:
Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.

Can you help me ?

Thanks in advance,

Best Answer

Do not initialize the matrix to zeros(): that requires numeric values instead of symbolic.

Try

matriz_N = sym(zeros(3, 6+4*k));

Related Solutions

MATLAB: Code only works in the command window

Looks like your while loop counter index, k, is going above the row count of matriz. For instance, check these simpler codes out to replicate your error and to fix it.


matriz = ones(1000, 3);
ano_ini = 1;
k = 1;
j = -1;
while matriz(k,3)==ano_ini %Error: Index exceeds matrix dimensions
    matriz(k,1)=j;
    k=k+1;
end
matriz = ones(1000, 3);
ano_ini = 1;
k = 1;
j = -1;
while matriz(k,3)==ano_ini
    matriz(k,1)=j;
    k=k+1;
    if k > size(matriz, 1); break; end  %break while loop before an error occurs
end

MATLAB: Error using vpasolve-Conversion to ‘sym’ from ‘struct’ is not possible.

Remove the (k) on the assignment to solv. The two lines after that already pull out the two variables and you do not need to store the solutions twice. Also the next two lines assume that you are using a scalar structure which would not be the case when you are assigning to solv(k)

Once you have assigned to just solv but before pulling out the components you should check if the solution is empty. You should also check in case there were multiple solutions, which is possible if the problem just happens to simplify to a polynomial.

Best Answer

Related Solutions

MATLAB: Code only works in the command window

MATLAB: Error using vpasolve-Conversion to ‘sym’ from ‘struct’ is not possible.

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