title: replace multiple values in a column for a single one
body: <p>I have a rather basic question. I have several values in a column that I would like to replace for a single one, for instance:</p>
  
  <p><code>a&lt;-data.frame(T=LETTERS[5:20],V=rnorm(16,10,1))</code></p>
  
  <p>and I would like to change all "E", "S", "T" in T for "AB", so I tried</p>
  
  <pre><code>a[a$T==c("E","S","T")]&lt;-"AB"
  </code></pre>
  
  <p>and it gives me several warnings, and ends up replacing all to "AB"</p>
  
  <p>I think it has something to do with levels and level's labels but I was not able to replace only some of the values, I would have to re-label each. Sorry for the trouble, and thanks for any help!</p>