make unique rows and append min value of some columns

Question

I have a data frame on R. I would like to get the unique rows based on the first three columns and also append the min value of the 4th column in each unique row.

dat <- tibble(
  x = c("a", "a", "k", "k"),
  y = c("a", "a", "l", "l"),
  z = c("e", "e", "m" ,"m"),
  t = c("4", "3", "8" ,"9"))

What I would like to see is below.

x	y	z	t
a	a	e	3
k	l	m	8

I believe there is a very easy way to do that but I can not see it at that moment.

Answer 1

We may call to apply() to find the unique rows values per row in dat. Then, we can used duplicated() to look for duplicates and use the negation ! to return rows that are not duplicates. We use which to obtain integers corresponding to the rows in dat that are not duplicates. Finally, use these integers (unique_rows) to extract the unique rows from dat. As such, we do not have to append.

unique_rows <- which(!duplicated(apply(dat[, 1:3], 1, unique)))
out <- dat[unique_rows, ]

Output

> out
  x y z t
1 a a e 4
3 k l m 8

Answer 2

Another way to deal with this would be to take minimum value of t column and keep remaining columns as group in aggregate function.

aggregate(t~., dat, min)

#  x y z t
#1 a a e 3
#2 k l m 8