eft;"> exercise </td>
   <td style="text-align:left;"> read_csv("data/ex_2.csv") |&gt;
  mutate(a = parse_integer(a)) </td>
  </tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-13 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv("data/ex_3.csv") </td>
  </tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-14 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv("data/ex_