I understand, you want to calculate the transfer function by substituting intermediate variables calculated with GR and frequency. I went through your live code file, and noticed the use of symbolic variables in tf( ) command. This is not supported. Instead, I recommend creating your ratios symbolic as shown below.
PA = ((Kpa*k*ti)*s + Kpa)/(ti*s + 1);
PI = (taui*s + 1)/(taui*s);
Now, in order to create the bode plots, you need numeric transfer functions. Kindly refer to the below link to obtain the required numeric transfer functions from your symbolic expressions.
