有数据如下，<br/>


<table cellspacing="0" cellpadding="0" border="0" width="192" style="border-collapse: collapse; width: 144pt;">
<col width="64" span="3" style="width: 48pt;"></col>
<tbody><tr height="20" style="height: 15pt;">
  <td height="20" width="64" style="height: 15pt; width: 48pt;">Sales1</td>
  <td width="64" style="width: 48pt;">Sales2</td>
  <td width="64" style="width: 48pt;">Sales3</td>
</tr>
<tr height="20" style="height: 15pt;">
  <td height="20" align="right" style="height: 15pt;">1</td>
  <td align="right">1</td>
  <td align="right">1</td>
</tr>
<tr height="20" style="height: 15pt;">
  <td height="20" align="right" style="height: 15pt;">0</td>
  <td align="right">3</td>
  <td align="right">1</td>
</tr>
<tr height="20" style="height: 15pt;">
  <td height="20" align="right" style="height: 15pt;">2</td>
  <td align="right">2</td>
  <td align="right">2</td>
</tr>
</tbody>
</table>
<br/>
现在想再生成一列，AvgSales。即新的数据为<br/>


<table cellspacing="0" cellpadding="0" border="0" width="256" style="border-collapse: collapse; width: 192pt;">
<col width="64" span="4" style="width: 48pt;"></col>
<tbody><tr height="20" style="height: 15pt;">
  <td height="20" width="64" style="height: 15pt; width: 48pt;">Sales1</td>
  <td width="64" style="width: 48pt;">Sales2</td>
  <td width="64" style="width: 48pt;">Sales3</td>
  <td width="64" style="width: 48pt;">AvgSales</td>
</tr>
<tr height="20" style="height: 15pt;">
  <td height="20" align="right" style="height: 15pt;">1</td>
  <td align="right">1</td>
  <td align="right">1</td>
  <td align="right">1</td>
</tr>
<tr height="20" style="height: 15pt;">
  <td height="20" align="right" style="height: 15pt;">0</td>
  <td align="right">3</td>
  <td align="right">1</td>
  <td align="right">1.333333</td>
</tr>
<tr height="20" style="height: 15pt;">
  <td height="20" align="right" style="height: 15pt;">2</td>
  <td align="right">2</td>
  <td align="right">2</td>
  <td align="right">2</td>
</tr>
</tbody>
</table>
<br/>
请问有没有诸如egen AvgSales=mean(Sales*)的办法？我的问题中不能简单的用gen AvgSales=(Sales1+Sales2+Sales3)/3，因为我的程序要处理多个数据。下一个数据中的列可能变成了<br/>
Sales2 Sales4 Sales5 Sales6<br/>
<br/>
请给予指导。万分感谢！