R 当第二个数据帧中存在匹配值时，替换数据帧列的值

我想用

df2$replacement

中的值替换

df1$colB

的值，其中

df1$colB

等于

df2$matches

df1 <- data.frame(colA = 1:10, colB = letters[1:10])

df2 <- data.frame(matches= letters[4:1], replacement= LETTERS [4:1])

---

我希望避免此任务的for循环解决方案。

您可以在

df1

和

df2

上执行

合并

，然后用

替换

替换

colB

值：

library(dplyr)
merge(df1, df2, by.x = "colB", by.y = "matches", all.x = T) %>% 
  mutate(colB = ifelse(!is.na(replacement), replacement, colB)) %>%  
  select(colA, colB)
   colA colB
1     1    A
2     2    B
3     3    C
4     4    D
5     5    e
6     6    f
7     7    g
8     8    h
9     9    i
10   10    j

---

您可以在

df1

和

df2

上执行

merge

，然后用

replacement

替换

colB

值：

library(dplyr)
merge(df1, df2, by.x = "colB", by.y = "matches", all.x = T) %>% 
  mutate(colB = ifelse(!is.na(replacement), replacement, colB)) %>%  
  select(colA, colB)
   colA colB
1     1    A
2     2    B
3     3    C
4     4    D
5     5    e
6     6    f
7     7    g
8     8    h
9     9    i
10   10    j

---

您可以在base R中使用

chartr

函数

# read in data with character vectors, not factors
df1 <- data.frame(colA = 1:10, colB = letters[1:10], stringsAsFactors=F)
df2 <- data.frame(matches= letters[4:1], replacement= LETTERS [4:1], stringsAsFactors=F)
df3 <- data.frame(colA =1:10, colB = c(LETTERS[1:4],letters[5:10]), stringsAsFactors=F)

# replace the characters with the desired characters
df1$colB <- chartr(paste(df2$matches, collapse=""), 
                   paste(df2$replacement, collapse=""), df1$colB)

#使用字符向量而非因子读入数据
df1您可以在base R中使用
chartr
函数

# read in data with character vectors, not factors
df1 <- data.frame(colA = 1:10, colB = letters[1:10], stringsAsFactors=F)
df2 <- data.frame(matches= letters[4:1], replacement= LETTERS [4:1], stringsAsFactors=F)
df3 <- data.frame(colA =1:10, colB = c(LETTERS[1:4],letters[5:10]), stringsAsFactors=F)

# replace the characters with the desired characters
df1$colB <- chartr(paste(df2$matches, collapse=""), 
                   paste(df2$replacement, collapse=""), df1$colB)

#使用字符向量而非因子读入数据
df1