title: From cross correlation to column format in R
body: <p>I have the following cross-correlation matrix:</p>
  <p>df =</p>
  <pre><code>   A B C
  A  1 7 1
  B  7 1 9
  C  1 9 1
  </code></pre>
  <p>and I would like to make it into the following format:</p>
  <pre><code>A B 7
  A C 1
  B C 9
  </code></pre>
  <p>any straightforward R code that can do such thing?</p>