CODEWITHSUNDEEP
rmatchsubset
Kim Phan
Kim Phan

Reputation: 17

Subset of dataframe for which 2 variables match another dataframe in R

I'm looking to obtain a subset of my first, larger, dataframe 'df1' by selecting rows which contain particular combinations in the first two variables, as specified in a smaller 'df2'. For example:

df1 <- data.frame(ID = c("A", "A", "A", "B", "B", "B"),
     day = c(1, 2, 2, 1, 2, 3), value = seq(4,9))

df1  # my actual df has 20 varables
ID day value
 A   1     4
 A   2     5
 A   2     6
 B   1     7
 B   2     8
 B   3     9

df2 <- data.frame(ID = c("A", "B"), day = c(2, 1))

df2 # this df remains at 2 variables
ID day
 A   2
 B   1

Where the output would be:

ID day value
 A   2     5
 A   2     6
 B   1     7

Any help wouldbe much appreciated, thanks!

Upvotes: 0

Views: 979

Answers (2)

J_F
J_F

Reputation: 10372

Here is a dplyr solution:

library("dplyr")
semi_join(df1, df2, by = c("ID", "day"))
#   ID day value
# 1  A   2     5
# 2  A   2     6
# 3  B   1     7

Upvotes: 0

Eric Watt
Eric Watt

Reputation: 3240

This is a good use of the merge function.

df1 <- data.frame(ID = c("A", "A", "A", "B", "B", "B"),
                  day = c(1, 2, 2, 1, 2, 3), value = seq(4,9))

df2 <- data.frame(ID = c("A", "B"), day = c(2, 1))

merge(df1,
      df2,
      by = c("ID", "day"))

Which gives output:

  ID day value
1  A   2     5
2  A   2     6
3  B   1     7

Upvotes: 2

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