title: Standardizing time columns in r
body: <p>I have 14 columns in a list that represent continuous timed trial where data was sampled at different times.</p>
  <p>my data looks like this:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th style="text-align: left;"></th>
  <th style="text-align: center;">time1</th>
  <th style="text-align: center;">time2</th>
  <th style="text-align: right;">time 3</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td style="text-align: left;">1</td>
  <td style="text-align: center;">3</td>
  <td style="text-align: center;">10</td>
  <td style="text-align: right;">15</td>
  </tr>
  <tr>
  <td style="text-align: left;">2</td>
  <td style="text-align: center;">4</td>
  <td style="text-align: center;">11</td>
  <td style="text-align: right;">16</td>
  </tr>
  <tr>
  <td style="text-align: left;">3</td>
  <td style="text-align: center;">5</td>
  <td style="text-align: center;">12</td>
  <td style="text-align: right;">17</td>
  </tr>
  <tr>
  <td style="text-align: left;">4</td>
  <td style="text-align: center;">6</td>
  <td style="text-align: center;"></td>
  <td style="text-align: right;">18</td>
  </tr>
  <tr>
  <td style="text-align: left;">5</td>
  <td style="text-align: center;">7</td>
  <td style="text-align: center;"></td>
  <td style="text-align: right;"></td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>how do I Standardize all 14 columns so the first row starts at zero and the last row has the  samples duration end time for each column . The freq =0.004 and each sample duration varies(~.5 seconds).</p>
  <p>So each row of data changes .004. Lets say the first row begins at 2.000 and the next is 2.004 so on and the end of the column is 2.504. So I need to change the first row to 0 and last row to .504. For all 14 columns in the list.</p>