title: How to convert a data column of class "list" to class "numeric"
body: <p>My data frame's name is <code>kineticsData</code> and the data column I'm trying to convert is <code>kineticsData$cellUptake</code></p>
  
  <p>When I run</p>
  
  <pre><code>sapply(kineticsData, class)
  </code></pre>
  
  <p>I get the following result for the data column of interest</p>
  
  <pre><code>cellUptake
  "factor"
  </code></pre>
  
  <p>I looked through a lot of old questions on here and I tried to convert my data column to <code>"numeric"</code> using their advice, but after running</p>
  
  <pre><code>as.numeric(levels(kineticsData$cellUptake))[kineticsData$cellUptake]
  </code></pre>
  
  <p>However, I still see</p>
  
  <pre><code>cellUptake
  "factor"
  </code></pre>
  
  <p>after running <code>sapply</code> again. Can anyone help me figure out what's going on?</p>
  
  <p>Also, I'm wondering if part of the problem is the fact that I'm importing the data in from an excel file where I've filled in the blank cells with a dash symbol: <code>-</code></p>
  
  <p>I noticed that the columns with numerical values but without any blank <code>-</code> cells automatically are imported as <code>"numeric"</code></p>