Error using sym>convertChar (line 1448)
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Hi everyone,
I get the error message:
"Error using sym>convertChar (line 1448) Character vectors and strings in the first argument can only specify a variable or number. To evaluate character vectors and strings representing symbolic expressions, use 'str2sym'.
Error in sym>tomupad (line 1214) S = convertChar(x);
Error in sym (line 211) S.s = tomupad(x);
Error in SolveExample>TurnEqIntoDEq (line 43) depVarsLong(k) = sym([char(depVars(k)) '(' char(indepVar) ')']);
Error in SolveExample (line 21) [dEq3, initEq3] = TurnEqIntoDEq(Eq1, [a b c], t, 0);"
when I run the attached code. What can I do?
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채택된 답변
Tiasa Ghosh
2018년 8월 13일
편집: Tiasa Ghosh
2018년 8월 13일
You have used the function subs() for substitution in your function TurnEqIntoDEq . The input to subs (L47 in your code file) is a string. But the function 'subs' expects a symbolic variable or expression. So in the parent file, convert the Eq1 to symbolic string with str2sym and then pass it to TurnEqIntoDEq function. Also, use str2sym for depVarsLong(k) and depVarsShort(k) in TurnEqIntoDEq. I have done the same to the file attached.
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추가 답변 (1개)
ahmed
2024년 5월 21일
syms s U Y
% Define the Laplace transform of u(t) and y(t)
U = laplace(sym('u(t)', 't'), s);
Y = laplace(sym('y(t)', 't'), s);
% Define the differential equation in Laplace domain
eqn = 6*s^2*U - 3*U + Y/s == -3*s^3*Y - Y;
% Solve for the Laplace transform of the output Y(s)
Y_s = solve(eqn, Y);
% Define the Laplace transform of the input, U(s)
U_s = laplace(sym('u(t)', 't'), s);
% Calculate the transfer function H(s) = Y(s) / U(s)
H_s = simplify(Y_s / U_s);
% Display the transfer function
disp('Transfer Function:');
disp(H_s);
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