tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-3 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> simple_csv &lt;- "
  x
  10
  .
  20
  30"

read_csv(simple_csv) </td>
  </tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-4 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv(simple_csv, col_types = list(x = col_double())) </td>
  </tr>
  <tr>
   <td style="text-align