library(pROC)
data(aSAH)
fit1 <- roc(aSAH$outcome, aSAH$s100b, levels = c("Good", "Poor"))
fit2 <- roc(aSAH$outcome, aSAH$ndka, levels = c("Good", "Poor"))
plot.roc(fit1, print.auc=T, print.auc.x=0.8, print.auc.y=0.8)
plot.roc(fit2, print.auc=T, print.auc.x=0.5, print.auc.y=0.5, add=T, col=2)