Question

我有两个数据帧
df1：

DAT1 DAT3     DAT4    ...
 1   this is  this is
 2   this is  this is
 3   this is  this is

df2：

DAT1 DAT3       DAT4      ... 
 1   a comment  a comment
 2   a comment  a comment
 3   a comment  a comment

我想找到一种方法将第二个数据框列（我知道我需要附加的列的名称和位置）附加到第一个，并获得具有以下内容的第一个数据框的更新版本：
df3：

DAT1 DAT3               DAT4               ... 
 1   this is a comment  this is a comment  
 2   this is a comment  this is a comment
 3   this is a comment  this is a comment

问题在于实际的数据帧具有许多行和列，因此for()循环实际上效率很低。

Answer 1

我们可以使用Map

cols <- c("DAT3", "DAT4")
df3 <- df1
df3[cols] <- Map(paste, df1[cols], df2[cols])

df3
#  DAT1              DAT3              DAT4
#1    1 this is a comment this is a comment
#2    2 this is a comment this is a comment
#3    3 this is a comment this is a comment

Answer 2

我们可以使用base R而无需循环

cols <- c("DAT3", "DAT4")     
df3 <- df1
df3[cols] <-matrix(paste(as.matrix(df1[-1]), as.matrix(df2[-1])), nrow = nrow(df1))
df3
#  DAT1              DAT3              DAT4
#1    1 this is a comment this is a comment
#2    2 this is a comment this is a comment
#3    3 this is a comment this is a comment

数据

df1 <- structure(list(DAT1 = 1:3, DAT3 = c("this is", "this is", "this is"
), DAT4 = c("this is", "this is", "this is")), class = "data.frame",
row.names = c(NA, 
-3L))

df2 <- structure(list(DAT1 = 1:3, DAT3 = c("a comment", "a comment", 
"a comment"), DAT4 = c("a comment", "a comment", "a comment")),
   class = "data.frame", row.names = c(NA, 
-3L))

Answer 3

如果订购了您的数据，我会做这样的事情：

#initiate the data.frame with the id
df3 <- data.frame(DAT1 = df1$DAT1)

#then run a for-loop with the names you know you need to concatenate
for (i in c('DAT3', 'DAT4')) {
  df3[[i]] <- paste(df1[[i]], df2[[i]])
}

for循环仅遍历名称。该代码的核心是paste，它是矢量化且快速的。因此，您不会遇到任何速度问题

df3
#  DAT1              DAT3              DAT4
#1    1 this-is a-comment this-is a-comment
#2    2 this-is a-comment this-is a-comment
#3    3 this-is a-comment this-is a-comment

Answer 4

dplyr版本

df1 %>% inner_join(df2, by = "DAT1") %>% rowwise() %>%
  mutate(DAT3 = paste(DAT3.x, DAT3.y, collapse = " "),
         DAT4 = paste(DAT4.x, DAT4.y, collapse = " ")) %>%
  select(everything(), -contains("."))

OutPut

# A tibble: 3 x 3
   DAT1 DAT3              DAT4             
  <dbl> <chr>             <chr>            
1     1 this is a comment this is a comment
2     2 this is a comment this is a comment
3     3 this is a comment this is a comment

有没有一种方法可以附加来自2个不同数据帧的列的值

4 个答案:

数据

OutPut