`jaccard` <-
function(x,y) 
{
ai <- (y[y>0]-x[y>0])!=y[y>0]
a <- length(ai[ai==TRUE])
b<-length(x[x>0])-a
c<-length(y[y>0])-a
jac<-a/(a+b+c)
return(jac)
}