title: Why do I get only one parameter from a statsmodels OLS fit
body: <p>Here is what I am doing:</p>
  
  <pre><code>$ python
  Python 2.7.6 (v2.7.6:3a1db0d2747e, Nov 10 2013, 00:42:54) 
  [GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
  &gt;&gt;&gt; import statsmodels.api as sm
  &gt;&gt;&gt; statsmodels.__version__
  '0.5.0'
  &gt;&gt;&gt; import numpy 
  &gt;&gt;&gt; y = numpy.array([1,2,3,4,5,6,7,8,9])
  &gt;&gt;&gt; X = numpy.array([1,1,2,2,3,3,4,4,5])
  &gt;&gt;&gt; res_ols = sm.OLS(y, X).fit()
  &gt;&gt;&gt; res_ols.params
  array([ 1.82352941])
  </code></pre>
  
  <p>I had expected an array with two elements?!?
  The intercept and the slope coefficient?</p>