1

Lot's of questions out there touching the topic of duplicate observations but none of them worked for me so far.

In this questions I learned how to select all duplicates from a vector. 

# vector
id <- c("a","b","b","c","c","c","d","d","d","d")

#To return ALL duplicated values by specifying fromLast argument:
id[duplicated(id) | duplicated(id, fromLast=TRUE)]
## [1] "b" "b" "c" "c" "c" "d" "d" "d" "d"

#Yet another way to return ALL duplicated values, using %in% operator:
id[id %in% unique(id[duplicated(id)])]
## [1] "b" "b" "c" "c" "c" "d" "d" "d" "d"

Now having a data frame like this one:

dat <- data.frame(x = c(1, 1, 2, 2, 3), 
                  y = c(5, 5, 6, 7, 8), 
                  z = c('a', 'b', 'c', 'd', 'e'))

How could I select all observations that simultaneously have duplicate values of x and y, irrespective of z?

MichaelChirico
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radek
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  • If the word `simultaneously` has some meaning , none of the answers below has taken that into consideration. If it does not then it is duplicate of the above question marked by @thelatemail. – Ronak Shah Nov 22 '17 at 02:57
  • @RonakShah perhaps it wasn't greatest choice of word and didn't mean more than `in the same time` – radek Nov 22 '17 at 03:22
  • @thelatemail I missed this one! :/ Indeed does what I need too so if the answers are duplicate the question could be closed I guess. – radek Nov 22 '17 at 03:23

3 Answers3

5

Another option using dplyr

library(dplyr)
dat %>% group_by(x,y) %>% filter(n()>1) 

# A tibble: 2 x 3
#     x     y      z
#   <dbl> <dbl> <fctr>
#1    1     5      a
#2    1     5      b
Santosh M.
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4

You can use data.table like so:

library(data.table)
setDT(dat)
# selects all (x,y) pairs that occur more than once
dat[ , if (.N > 1L) .SD, by = .(x, y)]
MichaelChirico
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2

In base R 

dat[ave(paste(dat$x,dat$y),dat$y,FUN=function(x) length(x))>1,]
  x y z
1 1 5 a
2 1 5 b
BENY
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