title: Updating a subset of a dataframe
body: <p>I have a dataframe as such</p>
  
  <pre><code>col.1 &lt;- c("a", "b", "c", "d", "e", "b", "c")
  col.2 &lt;- c(22, 33, 55, 66, 66, 22, 54)
  df &lt;- data.frame(col.1, col.2)
  </code></pre>
  
  <p>and I would like to update <code>col.2</code> to 100 when the <code>df$col.1</code> matches the <code>search.df</code></p>
  
  <pre><code>search.df &lt;- c("b", "d")
  </code></pre>
  
  <p>In fact I have <code>dataframe</code> of 1k+ rows and my <code>search.df</code> has 16 elements. I know some SQL and I can't find a straightforward update in R.</p>