title: Get access to the first row of a list in R
body: <p>Consider a list in R, for example</p>
  
  <pre><code>A=list()
  A[[1]]=c(1,2)
  A[[2]]=c(3,4)
  </code></pre>
  
  <p>Is it possible to return a vector which gives the first element of each entry of the list (here <code>c(1,3)</code>)?</p>
  
  <p>And as a extension: What, if the elements of the list are not just vectors but matrices. Is it possible to get the vector that contains the first element of the second row for each matrix?</p>