title: Gaussian Mixture Model clustering in sparklyr
body: <p>I'm trying to cluster my data using Gaussian Mixture Model in sparklyr:</p>
  
  <pre><code>ml_gaussian_mixture(formula= ~ var1 + var2 + var3 + var4 + var5, k = 5)
  </code></pre>
  
  <p>However, calling this function doesn't return a metric to evaluate the number of clusters as <code>ml_kmeans()</code> does (this function returns WSSSE).
  Is there a way to get the Silhouette score or BIC for <code>ml_gaussian_mixture()</code> in sparklyr ?</p>