title: Concatenate list elements into a date.frame in R
body: <p>I have an Excel file with several sheets, all containing the same data structure. I'm using readxl to read the sheets, and I store these results in a list, on sheet as one element. I'd now like to concatenate these into one dataframe. My structure after reading the data is the same as in the example list below (I've omitted the reading XLS part for clarity)</p>
  
  <pre><code>example_list = list(sheet1=tibble(A=c(1,2), B=c(3,4)), sheet2 = tibble(A=c  (5,6), B=c(7,8)))
  example_list
   $sheet1
   # A tibble: 2 x 2
        A     B
     &lt;dbl&gt; &lt;dbl&gt;
  1     1     3
  2     2     4
  
  $sheet2
  # A tibble: 2 x 2
        A     B
    &lt;dbl&gt; &lt;dbl&gt;
  1     5     7
  2     6     8
  </code></pre>
  
  <p>My result should look like this:</p>
  
  <pre><code># A tibble: 4 x 2
        A     B
    &lt;dbl&gt; &lt;dbl&gt;
  1     1     3
  2     2     4
  3     5     7
  4     6     8
  </code></pre>
  
  <p>I tried <code>flatten(example_list)</code> but this did not give me the desired result. </p>