R 기초문법 - 데이터 프레임 병합

• 데이터프레임 생성

DF2 = data.frame(
    A = c(1,2,3),
    B = c(4,5,6)
)

DF2

  A B
1 1 4
2 2 5
3 3 6

DF3 = data.frame(
  A = c(5,4,1),
  B = c(3,2,1)
)

DF3

  A B
1 5 3
2 4 2
3 1 1

• 행 기준 병합 - rbind()

rbind(DF2,DF3)

  A B
1 1 4
2 2 5
3 3 6
4 5 3
5 4 2
6 1 1

• 열 기준 병합 - cbind()

#데이터프레임 생성
DF4 = data.frame(
  A = c(1,2,3),
  B = c(4,5,6)
)

DF4

  A B
1 1 4
2 2 5
3 3 6

DF5 = data.frame(
  C = c(4,5,6),
  D = c(7,8,9)
)

DF5

  C D
1 4 7
2 5 8
3 6 9

cbind(DF4,DF5)

  A B C D
1 1 4 4 7
2 2 5 5 8
3 3 6 6 9

• key 기준 병합 - merge()

DF6 = data.frame(
  Key = c("A","B","C","D","E"),
  A = c(1,2,3,4,5)
)

DF6

  Key A
1   A 1
2   B 2
3   C 3
4   D 4
5   E 5

DF7 = data.frame(
  Key = c("C","D","E","F","G"),
  B = c(4,1,2,3,4)
)

DF7

  Key B
1   C 4
2   D 1
3   E 2
4   F 3
5   G 4

# all = TRUE

DF8 = merge(DF6, DF7, by = "Key",
            all = TRUE)

DF8

  Key  A  B
1   A  1 NA
2   B  2 NA
3   C  3  4
4   D  4  1
5   E  5  2
6   F NA  3
7   G NA  4

# all.x = TRUE

DF9 = merge(DF6, DF7, by = "Key",
            all.x = TRUE)

DF9

  Key A  B
1   A 1 NA
2   B 2 NA
3   C 3  4
4   D 4  1
5   E 5  2

# all.y = TRUE

DF10 = merge(DF6, DF7, by = "Key",
            all.y = TRUE)

DF10

  Key  A B
1   C  3 4
2   D  4 1
3   E  5 2
4   F NA 3
5   G NA 4

• key 변수 이름이 다른 경우

DF11 = data.frame(
  Key.x = c("A","B","C","D","E"),
  A = c(1,2,3,4,5)
)

DF11

  Key.x A
1     A 1
2     B 2
3     C 3
4     D 4
5     E 5

DF12 = data.frame(
  Key.y = c("C","D","E","F","G"),
  B = c(4,1,2,3,4)
)

DF13 = merge(DF11, DF12,
             by.x = "Key.x", by.y = "Key.y")

DF13

  Key.x A B
1     C 3 4
2     D 4 1
3     E 5 2