Create a new dataframe according to the contrast between two similar df [duplicate]

Question

I have a dataframe made like this:

  X Y  Z T
  1 2  4 2
  3 2  1 4
  7 5 NA 3

After several steps (not important which one) i obtained this df:

  X Y Z T
  1 2 4 2
  3 2 NA 4
  7 5 NA 3

i want to obtain a new dataframe made by only the rows which didn't change during the steps; the result would be this one:

 X  Y  Z  T
 1  2  4  2
 7  5  NA 3

How could I do?

Answer 1

Another dplyr solution: semi_join.

dt1 %>% semi_join(dt2, by = colnames(.))
  X Y  Z T
1 1 2  4 2
2 7 5 NA 3

Data

dt1 <- read.table(text = "X Y  Z T
  1 2  4 2
  3 2  1 4
  7 5 NA 3",
                  header = TRUE, stringsAsFactors = FALSE)

dt2 <- read.table(text = "  X Y Z T
  1 2 4 2
                  3 2 NA 4
                  7 5 NA 3",
                  header = TRUE, stringsAsFactors = FALSE)

Answer 2

You can use dplyr's intersect function:

library(dplyr)
intersect(d1, d2)
#  X Y  Z T
#1 1 2  4 2
#2 7 5 NA 3

This is a data.frame-equivalent of base R's intersect function.

In case you're working with data.tables, that package also provides such a function:

library(data.table)
setDT(d1)
setDT(d2)
fintersect(d1, d2)
#   X Y  Z T
#1: 1 2  4 2
#2: 7 5 NA 3