title: Remove quotes from factors of a data frame
body: <p>I have a data frame that I've <code>discretized</code> using <code>RWeka</code>. RWeka's discretization creates bins with single quotes in them. Although they are not causing any problems, while plotting it looks ugly to have a variable with <code>'All'</code> category. </p>
  
  <p>Here's the discretized data frame:</p>
  
  <pre><code>structure(list(outlook = structure(c(1L, 1L, 2L, 3L, 3L, 3L, 
  2L, 1L, 1L, 3L, 1L, 2L, 2L, 3L), .Label = c("sunny", "overcast", 
  "rainy"), class = "factor"), temperature = structure(c(1L, 1L, 
  1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "'All'", class = "factor"), 
  humidity = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
  1L, 1L, 1L, 1L, 1L), .Label = "'All'", class = "factor"), 
  windy = c(FALSE, TRUE, FALSE, FALSE, FALSE, TRUE, TRUE, FALSE, 
  FALSE, FALSE, TRUE, TRUE, FALSE, TRUE), play = structure(c(2L, 
  2L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 2L), .Label = c("yes", 
  "no"), class = "factor")), .Names = c("outlook", "temperature", 
  "humidity", "windy", "play"), row.names = c(NA, -14L), class = "data.frame")
  </code></pre>
  
  <p>How can I remove the single quotes from the data and recreate the factors?</p>