title: python scikit-learn clustering with missing data
body: <p>I want to cluster data with missing columns. Doing it manually I would calculate the distance in case of a missing column simply without this column.</p>
  
  <p>With scikit-learn, missing data is not possible. There is also no chance to specify a user distance function.</p>
  
  <p>Is there any chance to cluster with missing data?</p>
  
  <p>Example data:</p>
  
  <pre><code>n_samples = 1500
  noise = 0.05  
  X, _ = make_swiss_roll(n_samples, noise)
  
  rnd = np.random.rand(X.shape[0],X.shape[1]) 
  X[rnd&lt;0.1] = np.nan
  </code></pre>