title: Sum with particular condition
body: <p>I would like to know some information, it is possible make a group by with this particular condition:</p>
  <ul>
  <li>Column Sepal.length take the first value;</li>
  <li>Sum the column that began with Petal</li>
  <li>Not select Sepal.Width</li>
  </ul>
  <p>I have try this but I doesn't work:</p>
  <pre><code>m &lt;- iris
      
  m %&gt;% 
    group_by(Species) %&gt;% 
    summarise(across(starts_with(&quot;Petal&quot;), sum)) %&gt;% 
    summarise(F = first(Sepal.length))  # first for each Species
  </code></pre>