[R] Merge

[R] Merge Start

BioinformaticsAndMe

R Merge?

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: R에서는 두 개의 data.frame을 병합하기 위해, Merge 함수를 사용

*데이터프레임들은 최소 1개 이상의 동일한 column(열)을 가져야 함

: merge(x, y, by, all)

* x - 데이터프레임1

* y - 데이터프레임2

* by - 공통된 column (동일 변수)

* all - Merging의 형태 (default값=FALSE)

# 데이터 준비 (첫번째 data.frame)
df1 = data.frame(CustomerId = c(1:6), Product = c(rep("Oven", 3), rep("Television", 3)))
df1
  CustomerId    Product
1          1       Oven
2          2       Oven
3          3       Oven
4          4 Television
5          5 Television
6          6 Television

# 데이터 준비 (두번째 data.frame)
df2 = data.frame(CustomerId = c(2, 4, 6), State = c(rep("California", 2), rep("Texas", 1)))
df2
  CustomerId      State
1          2 California
2          4 California
3          6      Texas

Merge 형태

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1) Natural join: 두 데이터프레임에서 공통된 행만 유지 (all=FALSE)

2) Full outer join: 두 데이터프레임에서 모든 행을 유지 (all=TRUE)

3) Left outer join: 두 데이터프레임 중 좌측 x 프레임의 모든 행을 유지 (x=TRUE)

4) Right outer join: 두 데이터프레임 중 우측 y 프레임의 모든 행을 유지 (y=TRUE)

1) Natural join (Inner join)
df<-merge(x=df1,y=df2,by="CustomerId")
df
  CustomerId    Product      State
1          2       Oven California
2          4 Television California
3          6 Television      Texas

2) Full outer join 
df<-merge(x=df1,y=df2,by="CustomerId",all=TRUE)
df
  CustomerId    Product      State
1          1       Oven       <NA>
2          2       Oven California
3          3       Oven       <NA>
4          4 Television California
5          5 Television       <NA>
6          6 Television      Texas

3) Left outer join
df<-merge(x=df1,y=df2,by="CustomerId",all.x=TRUE)
df
  CustomerId    Product      State
1          1       Oven       <NA>
2          2       Oven California
3          3       Oven       <NA>
4          4 Television California
5          5 Television       <NA>
6          6 Television      Texas

4) Right outer join
df<-merge(x=df1,y=df2,by="CustomerId",all.y=TRUE)
df
  CustomerId    Product      State
1          2       Oven California
2          4 Television California
3          6 Television      Texas

#Reference

1) http://www.datasciencemadesimple.com/join-in-r-merge-in-r/

[R] Merge End

BioinformaticsAndMe