title: R: make symmetric matrix from lower diagonal
body: <p>I have a lower triangular of a matrix that I'm trying to convert to a dissim matrix and thus it needs to be symmetric.</p>
  
  <pre><code>print(rdf)
  
           X0        X1        X2        X3 X4
  0 0.0000000        NA        NA        NA NA
  1 0.5340909 0.0000000        NA        NA NA
  2 0.5340909 0.0000000 0.0000000        NA NA
  3 0.3200000 0.5227273 0.5227273 0.0000000 NA
  4 0.6263736 0.4945055 0.4945055 0.5384615  0
  
  library(gdata)
  upperTriangle(rdf) &lt;- lowerTriangle(rdf)
  isSymmetric(rdf)
         X0        X1        X2        X3        X4
  0 0.0000000 0.5340909 0.5340909 0.6263736 0.4945055
  1 0.5340909 0.0000000 0.3200000 0.0000000 0.5227273
  2 0.5340909 0.0000000 0.0000000 0.5227273 0.4945055
  3 0.3200000 0.5227273 0.5227273 0.0000000 0.5384615
  4 0.6263736 0.4945055 0.4945055 0.5384615 0.0000000
  [1] FALSE
  </code></pre>
  
  <p>What is going on? Note, I don't need to use gdata</p>