title: replace NA in a table with values in column with another table by conditions in R
body: <p>I have table 1 below:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>A</th>
  <th>B</th>
  <th>C</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>M</td>
  <td>12</td>
  </tr>
  <tr>
  <td>2</td>
  <td>F</td>
  <td>13</td>
  </tr>
  <tr>
  <td>3</td>
  <td>F</td>
  <td>NA</td>
  </tr>
  <tr>
  <td>5</td>
  <td>M</td>
  <td>17</td>
  </tr>
  <tr>
  <td>6</td>
  <td>F</td>
  <td>NA</td>
  </tr>
  <tr>
  <td>7</td>
  <td>M</td>
  <td>NA</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>And table2:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>A</th>
  <th>B</th>
  <th>C</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>3</td>
  <td>F</td>
  <td>11</td>
  </tr>
  <tr>
  <td>6</td>
  <td>F</td>
  <td>19</td>
  </tr>
  <tr>
  <td>7</td>
  <td>M</td>
  <td>15</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I would like to replace the NA value in column C from table 1 with the value in column C from table 2 based on column A and column B in both tables 1 and 2.</p>
  <p>How to write code in R?</p>