title: Replace NA values by row means
body: <p>I want to replace my NA values from a matrix acquired by :</p>
  
  <pre><code>read.table(…)
  </code></pre>
  
  <p>Those values should be the mean of the corresponding row.</p>
  
  <p>I.e, the following row of the table :</p>
  
  <pre><code>1 2 1 NA 2 1 1 2
  </code></pre>
  
  <p>would become</p>
  
  <pre><code>1 2 1 1.43 2 1 2
  </code></pre>
  
  <p>Thank you.</p>