<p>我有一个类似的数据帧:</p>
<pre><code>Key Departure Species1 Species2 Status
1 R Carlan Carlan D
1 R Scival Carex C
2 R Carlan Scival D
2 R Scival Bougra C
3 D Carlan Carlan D
3 D Scival Scival C
</code></pre>
<p>我想计算给定的<code>Departure</code>和<code>D</code>的<code>C</code>中每个唯一的<code>Species1</code>的出现次数</p>
<p>我想要的输出是:</p>
^{pr2}$