ols(a=col_double(), b = col_double(), c = col_double())) </td>
  </tr>
  <tr>
   <td style="text-align:left;"> reading-data-from-a-file-18 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv(file = "data/test_5.csv", na=".") </td>
  </tr>
  <tr>
   <td style="text-align:left;"> reading-data-from-a-file-19 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv("data/test_6.csv", comment = "#") </td>
  </tr>
  <tr