title: Matlab perfcurve labels formatting?
body: <p>I want to create a ROC curve in Matlab using the <code>perfcurve</code> function (it's for logistic regression similar as illustrated <a href="http://www.mathworks.co.uk/help/stats/perfcurve.html" rel="nofollow">in this example (bottom of page)</a>). I have 150 datapoints (binary data), but they are neither positive nor negative classes; they are the number of positive observations within the particular datapoint.</p>
  
  <p>Example (random data to illustrate):</p>
  
  <pre><code>datapoint   +ve observations    total observations
  1               23                  35
  2               27                  41
  3               23                  36
  4               18                  29
  5               19                  39
  6               21                  41
  7               24                  40
  8               29                  36
  9               38                  45
  10              12                  32
  </code></pre>
  
  <p>The example illustrated <a href="http://www.mathworks.co.uk/help/stats/perfcurve.html" rel="nofollow">on mathworks (bottom of page)</a> only demonstrates how to create labels for data rows that correspond either solely to positive or negative classes.</p>
  
  <p>For</p>
  
  <pre><code>[X,Y,T,AUC] = perfcurve(labels,scores,posclass)
  </code></pre>
  
  <p>how do I have to format my labels and posclass in order to make the ROC curve plot work?</p>
  
  <p>Thank you very much in advance.</p>