title: How to compute AUC with ROCR package
body: <p>I have fitted a SVM model and created the ROC curve with ROCR package. How can I compute the Area Under the Curve (AUC)?   </p>
  
  <pre><code>set.seed(1)
  tune.out=tune(svm ,Negative~.-Positive, data=trainSparse, kernel ="radial",ranges=list(cost=c(0.1,1,10,100,1000),gamma=c(0.5,1,2,3,4) ))
  summary(tune.out)
  best=tune.out$best.model
  
  ##prediction on the test set
  ypred = predict(best,testSparse, type = "class")
  table(testSparse$Negative,ypred)
  
  ###Roc curve
  yhat.opt = predict(best,testSparse,decision.values = TRUE)
  fitted.opt = attributes(yhat.opt)$decision.values
  rocplot(fitted.opt,testSparse ["Negative"], main = "Test Data")## 
  </code></pre>