title: R remove duplicate spatial points according an attribute
body: <p>In R I have a SpatialPointsDataFrame whit duplicated point (coordinates and attributes), I would like to remove all point with same data ...</p>
  
  <p>I have find in the <code>sp</code> package the <code>remove.duplicates()</code> function but it seems to remove only on location ...  Is there another way?</p>
  
  <p>thank you </p>
  
  <p>E.</p>