title: Renaming row values in gt() tables
body: <p>I'm trying to remove string from at gt() table, but without success.
  In my table I want multiple column names/titles covering two columns named &quot;Day 0&quot;, &quot;Day 4&quot;, &quot;Day 10&quot;, &quot;Day 17&quot; and sub columns named &quot;mean&quot; and &quot;se&quot;. Probably easier to understand when looking at the data.</p>
  <p>What I want right now is to remove the &quot;day 0&quot; (or e.g. &quot;day 4&quot;) from the sub column.
  Any suggestions?</p>
  <p>My code:</p>
  <pre><code>library(gt)
  
  gt(mean_se)%&gt;%
    tab_spanner(label = &quot;Day 0&quot;, columns = matches(&quot;0&quot;)) %&gt;%
    tab_spanner(label = &quot;Day 4&quot;, columns = matches(&quot;4&quot;)) %&gt;%
    tab_spanner(label = &quot;Day 10&quot;, columns = matches(&quot;10&quot;)) %&gt;%
    tab_spanner(label = &quot;Day 17&quot;, columns = matches(&quot;17&quot;)) %&gt;%
    tab_header(
      title = md(&quot;Biogenic volatile organic compound emissions&quot;))
    
    # str_remove(mean_se, &quot;day 0&quot;)
    # rename(&quot;mean&quot;==&quot;mean day 0&quot;)
  </code></pre>
  <p>Here's the data:</p>
  <pre><code>mean_se &lt;- structure(list(mass = c(&quot;i.x33.031&quot;, &quot;i.x35.034&quot;, &quot;i.x36.017&quot;, 
  &quot;i.x39.959&quot;, &quot;i.x40.023&quot;), `mean day 0` = c(&quot;241.82&quot;, &quot;0.36&quot;, 
  &quot;1.78&quot;, &quot;0.2&quot;, &quot;1.82&quot;), `se day 0` = c(&quot;241.82&quot;, &quot;0.36&quot;, &quot;1.78&quot;, 
  &quot;0.2&quot;, &quot;1.82&quot;), `mean day 4` = c(&quot;32.94&quot;, &quot;0.14&quot;, &quot;0&quot;, &quot;0&quot;, &quot;1.74&quot;
  ), `se day 4` = c(&quot;32.94&quot;, &quot;0.14&quot;, &quot;0&quot;, &quot;0&quot;, &quot;1.74&quot;), `mean day 10` = c(&quot;266.28&quot;, 
  &quot;0.6&quot;, &quot;0&quot;, &quot;0&quot;, &quot;1.58&quot;), `se day 10` = c(&quot;266.28&quot;, &quot;0.6&quot;, &quot;0&quot;, 
  &quot;0&quot;, &quot;1.58&quot;), `mean day 17` = c(&quot;451.4&quot;, &quot;0.48&quot;, &quot;0&quot;, &quot;0&quot;, &quot;2.94&quot;
  ), `se day 17` = c(&quot;451.4&quot;, &quot;0.48&quot;, &quot;0&quot;, &quot;0&quot;, &quot;2.94&quot;)), row.names = c(NA, 
  -5L), class = &quot;data.frame&quot;)
  </code></pre>