Consider these examples :
(mydata <- data.frame(surname=c(rep(LETTERS[1:5],2),"E"),
firstname=c(rep(letters[1:4],2),"d","a","x"),
postcode=c(rep(1:3,3),1,1)))
library(dplyr)
# dupliate over named variables only , i.e. surname & firstname
group_by(
mydata,
surname,
firstname
) %>%
mutate(
n = n()
) %>%
filter(n > 1)
#duplicated over postcode
group_by(
mydata,
postcode
) %>%
mutate(
n = n()
) %>%
filter(n > 1)
#surname or first name are the same and postcode is also the same
(surname_and_postcode_dup <-
group_by(
mydata,
surname,postcode) %>%
mutate(
n = n()
) %>%
filter(n > 1) )
(firstname_and_postcode_dup <-
group_by(
mydata,
firstname,postcode) %>%
mutate(
n = n()
) %>%
filter(n > 1))
(sur_or_first_and_post <-
bind_rows(surname_and_postcode_dup,
firstname_and_postcode_dup))