title: Set ordering of factor levels for multiple columns in a data frame
body: <p>I've loaded data from a CSV file into a data frame. Each column represents a survey question, and all of the answers are on a five-point Likert scale, with the labels:  ("None", "Low", "Medium", "High", "Very High").</p>
  
  <p>When I read in the data initially, R correctly interprets those values as factors but doesn't know what the ordering should be. I want to specify what the ordering is for the values so I can do some numerical calculations. I thought the following code would work:</p>
  
  <pre><code>X &lt;- read.csv('..')
  likerts &lt;- data.frame(apply(X, 2, function(X){factor(X, 
               levels = c("None", "Low", "Medium", "High", "Very High"), 
               ordered = T)}))
  </code></pre>
  
  <p>What happens instead is that all of the level data gets converted into strings. How do I do this correctly?</p>