R equivalent of SQL SELECT COUNT(*) ... GROUP BY

Question

I'm trying to find how to count the number of integers of each type in a vector. Eg, how many 1, 2, and 3 are there (without hard-coding == 1,2,3):

test_vec = c(1,2,3,1,2,1,2,1,1,1,2,1,3,1,2,3,2,1,2,1,3)

And, how to identify that I added some 4s to the vector and count them?

test_vec = c(test_vec,4,4,4)

I could do this with range() and a loop, but wondered if there is a general vectorised solution?

Edit: not the same question as this because that question doesn't ask about a generalised table situation (though the answers sensibly suggests it) but rather checking hard-coded equality sum(test_vec==x)

Answer 1

aggregate is very handy in this situation

> aggregate(data.frame(count = test_vec), list(value = test_vec), length)

  value count
1     1    10
2     2     7
3     3     4

Answer 2

you can use table

table(test_vec)
test_vec
 1  2  3 
10  7  4