Getting unique rows of a table and their numbers

Question

I have a dataframe:

id  y   z
oX  79  100
oX  23  46
oX  10  29
uM  12  90
uT  43  50
uT  13  99

I would like to keeep unique rows based on

Answer 1

this will do what you want :

> as.data.frame(table(a$id))
  Var1 Freq
1   oX    3
2   uM    1
3   uT    2