roc<-
function(pred ,y, cp=seq(0,1,.05), plots=1){
if(any(sort(unique(y))!= c(0,1))) stop("y must be 0/1")
auc <- function(x,y)(mean(rank(x)[y == 1]) - (sum(y) + 1)/2)/(length(x) - sum(y))
l<-length(cp)
sens<-vector(length=l)
espe<-vector(length=l)
for (i in 1:l){
   sens[i]<-sum(y==1 & pred>cp[i])/sum(y==1)
   espe[i]<-sum(y==0 & pred<=cp[i])/sum(y==0)
}
if(plots==1) par(mfrow=c(1,2))
      plot(cp,sens,type='l',lty=1)
      lines(cp,espe,lty=2)
      legend(.35,.15,c("sens","espe"),lty=c(1,2))
if (plots==2)      windows()
      plot(1-espe,sens,type='l',lty=1)
      text(.5,.3,paste("AUC=", round(auc(pred,y)[1],3)))
      cbind(cp,sens,espe)
}