Remove duplicated rows

Question

I have read a CSV file into an R data.frame. Some of the rows have the same element in one of the columns. I would like to remove rows that are duplicates in th

Answer 1

This problem can also be solved by selecting first row from each group where the group are the columns based on which we want to select unique values (in the example shared it is just 1st column).

Using base R :

subset(df, ave(V2, V1, FUN = seq_along) == 1)

#                      V1  V2 V3     V4 V5
#1 platform_external_dbus 202 16 google  1

In dplyr

library(dplyr)
df %>% group_by(V1) %>% slice(1L)

Or using data.table

library(data.table)
setDT(df)[, .SD[1L], by = V1]

If we need to find out unique rows based on multiple columns just add those column names in grouping part for each of the above answer.

data

df <- structure(list(V1 = structure(c(1L, 1L, 1L, 1L, 1L), 
.Label = "platform_external_dbus", class = "factor"), 
V2 = c(202L, 202L, 202L, 202L, 202L), V3 = c(16L, 16L, 16L, 
16L, 16L), V4 = structure(c(1L, 4L, 3L, 5L, 2L), .Label = c("google", 
"hughsie", "localhost", "space-ghost.verbum", "users.sourceforge"
), class = "factor"), V5 = c(1L, 1L, 1L, 8L, 1L)), class = "data.frame", 
row.names = c(NA, -5L))