title: Specificity/Sensitivity vs cut-off points using pROC package
body: <p>I need to plot the following graph so I can choose the optimal threshold for a logistic regression model.</p>
  
  <p><a href="https://i.stack.imgur.com/YSW33.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YSW33.gif" alt="Plot of Sensitivity and Specificity as a function of the Cutoff"></a></p>
  
  <p>However I can't use the packages (epi and roc) which are used in many of the research I have done. I do have the package pROC. Is there anyway to plot the graph using this package. Also how else could I choose the optimal threshold? How does it work using only the ROC curve? </p>