x <-
c
(
"A"
,
"B"
,
"C"
,
"B"
,
"A"
,
"A"
,
"C"
,
"A"
,
"B"
,
"C"
,
"A"
)
y <-
c
(20,15,45,14,21,22,47,18,16,50,23)
z <-
c
(
"YOUNG"
,
"KID"
,
"OLD"
,
"KID"
,
"YOUNG"
,
"YOUNG"
,
"OLD"
,
"YOUNG"
,
"KID"
,
"OLD"
,
"YOUNG"
)
df <-
data.frame
(class=x,age=y,age_group=z)
df
aggregate
( age~age_group,df,
function
(x)
length
(
unique
(x)))