This function takes two vectors, calculates the area-under-the-curve (AUC), and calculates the difference between the two.
auc_diff(x, y)Numeric vector of the x-values
A numeric matrix
A numeric value of the difference between two groups, or a numeric vector of the AUC across vertices
If y has 2 columns, then each column should be the values for each
subject group. If y has multiple columns (e.g., equal to the number of
vertices of a graph), it will calculate the AUC for each column.