x1 x2 y1 y2
    2  1  2  4
    4  4  5  3
    7  5  3  4
    7  3  1  9

<table border="1" class="dataframe">
  <thead>
    <tr style="text-align: right;">
      <th></th>
      <th>x1</th>
      <th>y1</th>
      <th>y2</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>1</th>
      <td>122</td>
      <td>12</td>
    </tr>
  </tbody>
</table>