title: How to export data from ROCR package
body: <p>I am trying to export biometric data from an analysis using the ROCR package.  Here is the code that I've done so far:</p>
  
  <pre><code>pred = performance(Matching.Score,Distribution)
  perf = prediction(pred,"fnr", "fpr")
  
  An object of class “performance”
  
  Slot "x.name":
  
  [1] "False positive rate"
  
  Slot "y.name":
  
  [1] "False negative rate"
  
  Slot "alpha.name":
  
  [1] "Cutoff"
  
  Slot "x.values":
  
  [[1]]
  
  [1] 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
  [15] 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
    ......
  
  Slot "y.values":
  
  [[1]]
  
  [1] 1.00000 0.99999 0.99998 0.99997 0.99996 0.99995
  [15] 0.99986 0.99985 0.99984 0.99983 0.99982 0.99981
      ......
  
  Slot "alpha.values":
  
  [[1]]
  
  [1]  Inf      1.0427800 1.0221150 1.0056240 1.0032630 0.9999599
  [12] 0.9644779 0.9633058 0.9628996 0.9626501 0.9607665 0.9605930
      .......
  </code></pre>
  
  <p>This results in several Slots.  I would like to export the resulting values into a text file for Excel modification using: </p>
  
  <p><code>write(pred, "filename")</code></p>
  
  <p>However, when I try to write the file, I get an error stating:</p>
  
  <pre><code>Error in cat(list(...), file, sep, fill, labels, append) : 
    argument 1 (type 'S4') cannot be handled by 'cat'
  </code></pre>
  
  <p>Is there any way around this?</p>
  
  <p>I'd appreciate any advice.  Thank you! </p>
  
  <p>Matt Peterson</p>