I need to count the number of elements in vector x which equal any vector element in vector y.
From here I can count the number of elements in vector x which equal to value in scalar `y with code:
x <- c(4,23,4,23,5,43,54,56,657,67,67,435,
             453,435,324,34,456,56,567,65,34,435, 675)
sum(x == 67)
Question:  How to count the number of elements in vector x which equal any vector element in vector y?
 
     
    