Convert an upper to lower triangle matrix in r : <p>I looked inot several posts, but I still couldn't find a way to just transform an upper triangle matrix into a lower triangle matrix.</p>

<p>I just want this: </p>

<pre><code>    1   2   3
a   10  11  12
b       13  14
c           15
</code></pre>

<p>To become this:</p>

<pre><code>    a   b   c
1   10
2   11  13
3   12  14  15
</code></pre>
