In your landmark VG Nat. Biotech paper, I am having a little bit of difficulty understanding ROC curve result of Figure 2A. As far as I think of comparing alignment, there is true and false but no positive/negative. If the alignment position matches the true position, it is true; otherwise false. If I think all reads are positive, then the TPR + FPR = 1. Could you please help me understand how the positive or negative is defined? Thanks!