Find duplicated rows (based on 2 columns) in Data Frame in R

You can always try simply passing those first two columns to the function duplicated:

duplicated(dat[,1:2])

assuming your data frame is called dat. For more information, we can consult the help files for the duplicated function by typing ?duplicated at the console. This will provide the following sentences:

Determines which elements of a vector or data frame are duplicates of elements with smaller subscripts, and returns a logical vector indicating which elements (rows) are duplicates.

So duplicated returns a logical vector, which we can then use to extract a subset of dat:

ind <- duplicated(dat[,1:2])
dat[ind,]

or you can skip the separate assignment step and simply use:

dat[duplicated(dat[,1:2]),]

Here's a dplyr option for tagging duplicates based on two (or more) columns. In this case ric and date:

df <- data_frame(ric = c('S1A.PA', 'ABC.PA', 'EFG.PA', 'S1A.PA', 'ABC.PA', 'EFG.PA'),
                 date = c('2011-06-30 20:00:00', '2011-07-03 20:00:00', '2011-07-04 20:00:00', '2011-07-05 20:00:00', '2011-07-03 20:00:00', '2011-07-04 20:00:00'),
                 open = c(23.7, 24.31, 24.495, 24.23, 24.31, 24.495))

df %>% 
  group_by(ric, date) %>% 
  mutate(dupe = n()>1)
# A tibble: 6 x 4
# Groups:   ric, date [4]
  ric    date                 open dupe 
  <chr>  <chr>               <dbl> <lgl>
1 S1A.PA 2011-06-30 20:00:00  23.7 FALSE
2 ABC.PA 2011-07-03 20:00:00  24.3 TRUE 
3 EFG.PA 2011-07-04 20:00:00  24.5 TRUE 
4 S1A.PA 2011-07-05 20:00:00  24.2 FALSE
5 ABC.PA 2011-07-03 20:00:00  24.3 TRUE 
6 EFG.PA 2011-07-04 20:00:00  24.5 TRUE 

Easy way to get the information you want is to use dplyr.

yourDF %>% 
  group_by(RIC, Date) %>% 
  mutate(num_dups = n(), 
         dup_id = row_number()) %>% 
  ungroup() %>% 
  mutate(is_duplicated = dup_id > 1)

Using this:

• num_dups tells you how many times that particular combo is duplicated
• dup_id tells you which duplicate number that particular row is (e.g. 1st, 2nd, or 3rd, etc)
• is_duplicated gives you an easy condition you can filter on later to remove all the duplicate rows (e.g. filter(!is_duplicated)), though you could also use dup_id for this (e.g. filter(dup_id == 1))

dplyr is so much nicer for this sort of thing:

library(dplyr)
yourDataFrame %>%
    distinct(RIC, Date, .keep_all = TRUE)

(the ".keep_all is optional. if not used, it will return only the deduped 2 columns. when used, it returns the deduped whole data frame)