d>
   <td style="text-align:left;"> read_csv(
  "data/ex_2.csv",
  col_types = cols(.default = col_character())
) %&gt;%
  mutate(
    a = parse_integer(a),
    b = parse_date(b, format = "%Y%M%D")
  ) </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 sty