擅长:python、mysql、java
<p>使用<a href="https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.core.groupby.GroupBy.transform.html" rel="nofollow noreferrer">^{<cd1>}</a>:</p>
<pre><code>data['count'] = data.groupby('roi').roi.transform('size')
</code></pre>
<p>或<a href="https://pandas.pydata.org/pandas-docs/version/0.25/reference/api/pandas.Series.map.html" rel="nofollow noreferrer">^{<cd2>}</a>+<a href="https://pandas.pydata.org/pandas-docs/version/0.25/reference/api/pandas.Series.value_counts.html" rel="nofollow noreferrer">^{<cd3>}</a>:</p>
<pre><code>data['count']=data.roi.map(data.roi.value_counts())
</code></pre>