.html"><a href="data2file.html#-3"><i class="fa fa-check"></i><b>6.5</b> 总结</a></li>
</ul></li>
<li class="chapter" data-level="7" data-path="tidy.html"><a href="tidy.html"><i class="fa fa-check"></i><b>7</b> 数据清洗和准备</a><ul>
<li class="chapter" data-level="7.1" data-path="tidy.html"><a href="tidy.html#section-7.1"><i class="fa fa-check"></i><b>7.1</b> 处理缺失数据</a></li>
<li class="chapter" data-level="7.2" data-path="tidy.html"><a href="tidy.html#section-7.2"><i class="fa fa-check