I'm doing a cross validation using the leave-one-out method. I have a binary response and am using the boot package for R, and the cv.glm function. My problem is that I don't fully understand the "cost" part in this function. From what I can understand this is the function that decides whether an estimated value should be classified as a 1 or a 0, i.e the threshold value for the classification. Is this correct?
And, in the help in R they use this function for a binomial model:
cost <- function(r, pi = 0) mean(abs(r-pi) > 0.5). How do I interpret this function? so I can modify it correctly for my analysis.
Any help is appreciated, don't want to use a function I don't understand.