I am trying the Generate ROC operator after running different k-nn algorithms in the Anomaly Detection extension. However, I am getting a error message telling me " not found in labels. All worked fine when I was just using the k-nn algorithms. But when I added the "Generate ROC" operator in series after the k-nn, I got the error message. I am a newbie running RapidMiner 5.3.013. Is it how to generate the ROC curve? Also, how do I add different k-nn algorithms output to generate different ROC curves for each algorithm on the same graph to compare them. Many thanks!