title: change value from last column last row in R dataframe using dplyr
body: <p>I want to change the last column last value from R dataframe.</p>
  <p>I know I can use base R this way:</p>
  <pre><code>df[nrow(), ncol()] &lt;- &quot;my value&quot;
  </code></pre>
  <p>But I would like to use tidy approach</p>
  <p>What i tried so far:</p>
  <pre><code># the last row and column to mutate by name
  
  df %&gt;% slice(1) %&gt;% mutate(my_last_column=&quot;my value&quot;) 
  </code></pre>
  <p>But I really would like to do it without knowing the column name.</p>