R row_number() results in only 1s

I want to produce a table where each patient has a row number in order of highest RDI to lowest RDI.

Sample Data, RDItable:

SubjectID	RDI	SomeOtherCols
1004	100	x
1004	100	y
1004	100	z
1002	99.5	x
1002	99.5	y
1002	99.5	z
1001	85.1	x
1001	85.1	y
1001	85.1	z
1003	100	x
1003	100	y
1003	100	z

Here is what had worked for me in the past with minor adjustments (by including the RDI column)

attempt1<- RDItable %>% 
 distinct(SubjectID, RDI) %>% 
 arrange(desc(RDI)) %>% 
 mutate(row_id = row_number(RDI))

but this results in:

SubjectID	RDI	row_id
1004	100	1
1003	100	1
1002	99.5	1
1001	85.1	1

and I want each row to contain a different value:

SubjectID	RDI	row_id
1004	100	1
1003	100	2
1002	99.5	3
1001	85.1	4

Solution

It is possible that the data already had a rowwise attribute which makes the row_number() to return only 1 as there is only a single row per group. We may need to ungroup if that is the case

library(dplyr)
RDItable %>%
   ungroup %>%
   distinct(SubjectID, RDI) %>%
    arrange(desc(RDI)) %>% 
    mutate(row_id = row_number())

-output

  SubjectID   RDI row_id
1      1004 100.0      1
2      1003 100.0      2
3      1002  99.5      3
4      1001  85.1      4

The output can be replicated with rowwise attribute

> RDItable %>%
    rowwise %>% 
    distinct(SubjectID, RDI) %>%
    arrange(desc(RDI)) %>%
    mutate(row_id = row_number())
# A tibble: 4 × 3
# Rowwise: 
  SubjectID   RDI row_id
      <int> <dbl>  <int>
1      1004 100        1
2      1003 100        1
3      1002  99.5      1
4      1001  85.1      1