Is there an R function to use with top_n when scores are equal

Question

I'm doing correlations on school leaving scores and University scores. I use top_n to clean the school scores of retakes, but sometimes the poor candidate gets the same score on retake. How to eliminate these duplicates ?

  Studno  Math
     <int> <int>
 1 2105234    53
 2 2126745    10
 3 2126745    10
 4 2110897    41
 5 2344567    55
 6 2213467    63
 7 2314521    67
 8 2314521    40
 9 2123456    18
10 2123456    45

   duppymat1 %>% group_by ("Studno") %>% top_n(1,"Math")

This eliminates the two duplicates where scores are different, but how to code to eliminate one of the two that are equal ?

Answer 1

I tend to use row_number() == 1

for example:

require(tidyverse)

df <- tribble(
  ~ Studno,  ~ Math,
2105234,    53,
2126745,    10,
2126745,    10,
2110897,    41,
2344567,    55,
2213467,    63,
2314521,    67,
2314521,    40,
2123456,    18,
2123456,    45
)


df %>% group_by (Studno) %>% top_n(1,Math)

df %>% group_by(Studno) %>% filter(row_number(desc(Math))==1)

gives

# A tibble: 7 x 2
# Groups:   Studno [7]
   Studno  Math
    <dbl> <dbl>
1 2105234    53
2 2126745    10
3 2110897    41
4 2344567    55
5 2213467    63
6 2314521    67
7 2123456    45