Question

假设我有一个名为df的数据框：

df <- data.frame(
   A = 1:8, 
   B = rep(letters[1:4], each = 2),
   C = rep(1:2, 4)
)

  A B C
1 1 a 1
2 2 a 2
3 3 b 1
4 4 b 2
5 5 c 1
6 6 c 2
7 7 d 1
8 8 d 2

我希望交换B列中的值，b或c，但不是a或d时的值在另一列C上，即C = 1时。所以目标data.frame是df1：

 df1 <- data.frame(
  A = 1:8,
  B = c("a", "a", "c", "b", "b", "c", "d", "c"),
  C = rep(1:2, 4)      
)

  A B C
1 1 a 1
2 2 a 2
3 3 c 1
4 4 b 2
5 5 b 1
6 6 c 2
7 7 d 1
8 8 c 2

Answer 1

您可以尝试chartr('bc', 'cb', df$B) #[1] "a" "a" "c" "c" "b" "b" "d" "d"，

C == 1

要在df$B[df$C == 1] <- chartr('bc', 'cb', df$B[df$C == 1])上进行调整，然后

{{1}}

Answer 2

# this will work generally
ic <- df$B == 'c'
ib <- df$B == 'b'
df$B[ic] <- 'b'
df$B[ib] <- 'c'

> df
  A B
1 1 a
2 2 a
3 3 c
4 4 c
5 5 b
6 6 b
7 7 d
8 8 d

Answer 3

gsub("_", "", ifelse(df$B == "b", "_c", ifelse(df$B == "c", "_b", as.character(df$B))))
#[1] "a" "a" "c" "c" "b" "b" "d" "d"

Answer 4

dplyr提供recode一次替换多个值，如下所示。根据您问题中的新要求，我更新了以下代码，以提供所需的输出：

> library(dplyr)
> df
  A B C
1 1 a 1
2 2 a 2
3 3 b 1
4 4 b 2
5 5 c 1
6 6 c 2
7 7 d 1
8 8 d 2

> for(i in 1:nrow(df)) {
   if(df$C[i] == "1") {
     df$B[i] <- recode(df$B[i], 'b' = 'c', 'c' = 'b')
   }
 }

> df
  A B C
1 1 a 1
2 2 a 2
3 3 c 1
4 4 b 2
5 5 b 1
6 6 c 2
7 7 d 1
8 8 d 2

Answer 5

 a=which(df$B%in%letters[2:3]&df$C==1)
 df[a,2]=df[rev(a),2];df
   A B C
 1 1 a 1
 2 2 a 2
 3 3 c 1
 4 4 b 2
 5 5 b 1
 6 6 c 2
 7 7 d 1
 8 8 d 2

如何在一列中交换值的子集，但保持同一列中的其他值不变？

5 个答案: