Filtering the whole group contains min value

Question

I try to filter the group that contains min x value in them. But I would like to keep the entire group.

Similar post in here but not for min value filtering Remove groups that contain certain strings

So I try

  df <-data.frame(x=c(250,240,233,250,100,10,250,100,1),gr=gl(3,3))

> df
    x gr
1 250  1
2 240  1
3 233  1
4 250  2
5 100  2
6  10  2
7 250  3
8 100  3
9   1  3

    df%>%
    group_by(gr)%>%
    filter(all(x==min(x)))

Returning the empty df. Why ?

the expected output would be

    x  gr
7 250  3
8 100  3
9   1  3

Answer 1

You should using any instead of all

df%>%group_by(gr)%>%filter(any(x==min(df$x)))
# A tibble: 3 x 2
# Groups:   gr [1]
      x     gr
  <dbl> <fctr>
1   250      3
2   100      3
3     1      3

Answer 2

A base R approach could be finding the corresponding gr of minimum x and then filtering the dataframe based on that.

df[df$gr %in% df$gr[which.min(df$x)],]

#  x   gr
#7 250  3
#8 100  3
#9   1  3

---

Or similar to your and @Wen's approach using ave

df[ave(df$x, df$gr, FUN = function(i) any(i == min(df$x))) == 1, ]