title: Python statsmodels trouble getting fitted model parameters
body: <p>I'm using an AR model to fit my data and I think that I have done that successfully, but now I want to actually see what the fitted model parameters are and I am running into some trouble.  Here is my code</p>
  
  <pre><code>model=ar.AR(df['price'],freq='M')
  ar_res=model.fit(maxlags=50,ic='bic')
  </code></pre>
  
  <p>which runs without any error.  However when I try to print the model parameters with the following code</p>
  
  <pre><code>print ar_res.params
  </code></pre>
  
  <p>I get the error</p>
  
  <pre><code>AssertionError: Index length did not match values
  </code></pre>