title: How to convert dataframe to matrix without column names
body: <p>I would like to convert a dataframe into a numeric-only matrix.  My goal:</p>
  
  <blockquote>
    <p>num [1:3, 1:4] 1 2 3 1 2 3 1 2 3 1 ...</p>
  </blockquote>
  
  <p><strong><em>And that's all.</em></strong></p>
  
  <pre><code>alpha &lt;- beta &lt;- gamma &lt;- delta &lt;- c(1,2,3)
  df &lt;- data.frame(alpha, beta, gamma, delta, stringsAsFactors = FALSE)
  
  M1 &lt;- as.matrix(df, ncol = ncol(df))
  str(M1)
  
  M2 &lt;- data.matrix(df)
  str(M2)
  </code></pre>
  
  <blockquote>
    <p>num [1:3, 1:4] 1 2 3 1 2 3 1 2 3 1 ...
     - attr(*, "dimnames")=List of 2<br>
      ..$ : NULL<br>
      ..$ : chr [1:4] "alpha" "beta" "gamma" "delta"</p>
  </blockquote>
  
  <p>I can't for the life of me figure out how to do it without all the attributes.  I need the pure form as input to another method.</p>