I want to find the cut-off point for gender based on an anthropological measurement. I can draw the curves and I know that in case sensitivity and specificity are both similarly important, the point closest to the upper left corner of the frame (or if the curve is negative, the closest point to the lower right corner) should be determined as cut-off.
However, I don’t know whether there is any already implemented function in R or any other programs for determining this, simply? I just know SPSS doesn’t have such a function. Do you know any programs, or R which can do it via an already implemented function?
You want to compute the Youden Index, and find the highest one in your ROC curve.
library(pROC) data(aSAH) rocobj <- roc(aSAH$outcome, aSAH$s100b) coords(rocobj, "best") coords(rocobj, x="best", input="threshold", best.method="youden") # Same than last line