title: 'clusters' in igraph unable to find
body: <pre><code>g=get.adjacency(erdos.renyi.game(100,0.5))
  clusters(g)
  </code></pre>
  
  <blockquote>
    <p>Error in (function (classes, fdef, mtable)  :    unable to find an
    inherited method for function ‘clusters’ for signature ‘"dgCMatrix",
    "missing"’</p>
  </blockquote>
  
  <pre><code>clusters(graph.adjacency(g,mode='undirected',weighted=T))
  </code></pre>
  
  <blockquote>
    <p>Error in (function (classes, fdef, mtable)  :    unable to find an
    inherited method for function ‘clusters’ for signature ‘"igraph",
    "missing"’</p>
  </blockquote>
  
  <p>For some reason first it condsiders g as sparse matrix, then when I change it to proper graph objects, it just cannot find the funciton. Until few days ago it was working perfectly, and then on Friday after lunch it just stopped working and I started obtaining these error messages. I would be grateful to anyone that could have an idea about this issue. It seems the function is not in the package anymore, as when I search for it, it just does not appear to be there.</p>