title: clValid function to work for Big Data
body: <p>Package <code>clValid</code> reports validation measures for clustering results. The function returns an object of class <code>clValid</code>, which contains the clustering results in addition to the validation measures. The validation measures fall into three general categories: <code>internal</code>, <code>stability</code>, and <code>biological</code>.</p>
  
  <pre><code> clValid(obj, nClust, clMethods="hierarchical", validation="stability", maxitems=600, 
           metric="euclidean", method="average", neighbSize=10, ...)
  </code></pre>
  
  <p>Any idea how to tweak the above function so that it works on big data (i.e., <code>maxitems &gt;= 50000</code>)?</p>