Help with symbolic transfer function?

Hello,

I am trying to have an output that gives me a transfer function, given certain variables. Matlab is telling me the following: Error using tf (line 296) The values of the "Numerator" and "Denominator" properties must be row vectors or cell arrays of row vectors, where each vector is nonempty and containing numeric data. Type "help tf.num" or "help tf.den" for more information.

Is there anyway around assigning data to the variables, and still use the transfer function? Below is a copy of my code.

-Robert

CODE:

syms K1 K2 K3 I s

theta = (K1*K2)/I;

num = {theta};
den = {1 theta*K3 theta};

Gs = tf(num,den);

Answer 1

[Walter Roberson]

"Is there anyway around assigning data to the variables, and still use the transfer function?"

NO. tf() will never support symbolic parameters.

See https://www.mathworks.com/matlabcentral/answers/305339-how-to-create-a-transfer-function-with-gain-k#answer_236890 for a semi-detailed discussion of what is available.