Counting the number of elements with the values of x in a vector

You can just use table():

> a <- table(numbers)
> a
numbers
  4   5  23  34  43  54  56  65  67 324 435 453 456 567 657 
  2   1   2   2   1   1   2   1   2   1   3   1   1   1   1 

Then you can subset it:

> a[names(a)==435]
435 
  3

Or convert it into a data.frame if you’re more comfortable working with that:

> as.data.frame(table(numbers))
   numbers Freq
1        4    2
2        5    1
3       23    2
4       34    2
...