title: skmeans not producing silhouette plot in r
body: <p>I have clustered large dataset(~1m observations and ~200 features) with skmeans and I want to validate the results. The problem is that according to tutorial, skmeans produces object which is suitable for silhouette calculations, but if I follow the tutorial I get error message.Could somebody explain where does this error come from?Both objects are of the same class but plotting works for hparty,but not on my clustering.</p>
  
  <pre><code>class(hparty)
  [1] "skmeans" "pclust" 
  hparty
  A hard spherical k-means partition of 1504 objects into 5 classes.
  Class sizes: 311, 278, 131, 429, 355
  Call: skmeans(x = x, k = 5)
  class(seg.sk10)
  [1] "skmeans" "pclust" 
  seg.sk10
  A hard spherical k-means partition of 1488441 objects into 10 classes.
  Class sizes: 79007, 81885, 219730, 58998, 107383, 161908, 98570, 132689, 395367, 152904
  Call: skmeans(x = duom.1, k = k)
  plot(silhouette(seg.sk10))
  Error in FUN(left, right) : non-numeric argument to binary operator
  </code></pre>