R rowsum()

1 개요

R rowsum()

• "Give Column Sums Of A Matrix Or Data Frame, Based On A Grouping Variable"

R

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mat <- as.matrix(cbind(c(1,2,3,4),c(1,2,3,4)))
mat
##      [,1] [,2]
## [1,]    1    1
## [2,]    2    2
## [3,]    3    3
## [4,]    4    4

#### 그대로
rowsum(mat, c(1,2,3,4))
##   [,1] [,2]
## 1    1    1
## 2    2    2
## 3    3    3
## 4    4    4

## 1~2행 합산
rowsum(mat, c(1,1,2,3))
##   [,1] [,2]
## 1    3    3
## 2    3    3
## 3    4    4

## 2~4행 합산
rowsum(mat, c(1,2,2,2))
##   [,1] [,2]
## 1    1    1
## 2    9    9

rowsum()없이 합산

R

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mat <- as.matrix(cbind(c(1,2,3,4),c(1,2,3,4)))
#### 2~4행 합산
mat[2,] <- mat[2,] + mat[3,] + mat[4,] 
mat <- mat[-(3:4),]
mat
##      [,1] [,2]
## [1,]    1    1
## [2,]    9    9

2 같이 보기

• R tapply()
• R aggregate()
• R rowSums()

3 참고

• https://www.rdocumentation.org/packages/base/versions/3.6.1/topics/rowsum