title: How to calculate the mean of vectors from multiple lists?
body: <p>I have several lists containing vectors and I would like to obtain a single list, which elements are the mean vectors of the vectors of the initial lists. </p>
  
  <p>Example: Two initial lists</p>
  
  <pre><code>lt1 &lt;- list(a = c(1,2,3), b = c(2,5,10))
  lt2 &lt;- list(a = c(3,4,5), b = c(4,5,2))
  </code></pre>
  
  <p>And I would like to obtain</p>
  
  <pre><code>lt12 &lt;- list(a = c(2,3,4), b = c(3,5,6))
  </code></pre>
  
  <p>I tried with lapply and llply, but I always end up obtaining the mean of the  vector of each list.</p>