title: Appending the lists of two lists of lists
body: <p>I have two lists as follows:</p>
  <pre><code>list1 &lt;- list(c(`0` = 0L, `25` = 0L, `100` = 1L, `250` = 1L, `500` = 1L, 
                  `1000` = 1L, Infinity = 3L), c(`0` = 0L, `25` = 0L, `100` = 1L, 
                                                 `250` = 1L, `500` = 1L, Infinity = 4L))
  
  list2 &lt;- list(c(`0` = 0L, `25` = 0L, `100` = 0L, `250` = 2L, `500` = 1L, 
                  `1000` = 1L, Infinity = 3L), c(`0` = 0L, `25` = 0L, `100` = 1L, 
                                                 `250` = 1L, `500` = 1L, Infinity = 4L))
  </code></pre>
  <p>I would like to append <code>list2[[1]]</code> to <code>list1[[1]]</code> and append <code>list2[[2]]</code> to <code>list1[[2]]</code>. So that:</p>
  <pre><code>list_out &lt;- list(c(`0` = 0L, `25` = 0L, `100` = 1L, `250` = 1L, `500` = 1L, 
                  `1000` = 1L, Infinity = 3L, `0` = 0L, `25` = 0L, `100` = 0L, `250` = 2L, `500` = 1L, 
                  `1000` = 1L, Infinity = 3L), c(`0` = 0L, `25` = 0L, `100` = 1L, 
                                                 `250` = 1L, `500` = 1L, Infinity = 4L, `0` = 0L, `25` = 0L, `100` = 1L, 
                                                 `250` = 1L, `500` = 1L, Infinity = 4L))
  </code></pre>
  <p>Could anyone help me explain how should I do this?</p>