Truncating a dataframe according to count of vector elements

Question

I have a dataframe df, containing three vectors:

subject  condition  value
01       A          12
01       A          6
01       B          10
01            


        

Answer 1

Here's a dplyr solution -

df %>%
  group_by(subject, condition) %>%
  filter(row_number() < 3) %>%
  ungroup()

# A tibble: 8 x 3
  subject condition value
          
1 01      A            12
2 01      A             6
3 01      B            10
4 01      B             2
5 02      A             5
6 02      A            11
7 02      B             3
8 02      B             5