title: Use max on each element of a matrix
body: <pre><code>&gt; x &lt;- array(-10:10, dim=c(4,5))
  &gt; x
       [,1] [,2] [,3] [,4] [,5]
  [1,]  -10   -6   -2    2    6
  [2,]   -9   -5   -1    3    7
  [3,]   -8   -4    0    4    8
  [4,]   -7   -3    1    5    9
  </code></pre>
  
  <p>How do I apply "max(x, 0)" to each element so that I get this matrix:</p>
  
  <pre><code>     [,1] [,2] [,3] [,4] [,5]
  [1,]    0    0    0    2    6
  [2,]    0    0    0    3    7
  [3,]    0    0    0    4    8
  [4,]    0    0    1    5    9
  </code></pre>