title: Symbolic transfer function matlab
body: <p>I am trying to use transfer functions with symbolic values but I only returns errors.</p>
  
  <p>Is there a way to work with Laplace transformed in symbolic mode with MatLab?</p>
  
  <p>Here an example that I am trying to do and the MatLab message error:</p>
  
  <pre><code>&gt;&gt; syms Ki Kp Te R;
  &gt;&gt; s=tf('s');
  &gt;&gt; g=((Kp*s+Ki)/s)
  Error using sym&gt;tomupad (line 1014)
  Conversion to 'sym' from 'tf' is not possible.
  
  Error in sym (line 139)
              S.s = tomupad(x,'');
  
  Error in sym/privResolveArgs (line 823)
                      argout{k} = sym(arg);
  
  Error in sym/privBinaryOp (line 838)
              args = privResolveArgs(A, B);
  
  Error in  *  (line 216)
          X = privBinaryOp(A, B, 'symobj::mtimes');
  </code></pre>
  
  <p>I have tried some other forms to create a transfer function with no results:</p>
  
  <pre><code>&gt;&gt; sys=tf([Te],[0 Ki])
  Error using tf (line 287)
  The values of the "num" and "den" 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.
  </code></pre>