Skip to main content

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

2
  • @Riccardo If so, accept his answer by clicking a gray tick next to it. Commented Jul 21, 2011 at 16:33
  • 4
    one problem with this - column names take the numeric representation of the factor level. Commented May 20, 2013 at 13:46