Question

让我们假设两个数据帧：A和B包含如下数据：数据帧：数据帧：B

 ColA1   ColA2             ColB1      ColB2
  | Dog   | Lion              | Lion     | Lion
  | Lion  | Dog               | Cat      | NA
  | Zebra | Tiger             | Tiger    | Tiger
  | Bat   | Parrot            | Dog      | Dog

如果ColB1的动物存在于ColA1或ColA2中，则将来自＆＃39; ColB2＆＃39;的该动物的名称插入ColB2，否则插入NA。

而不是两次运行ifelse函数两次：

B$ColB2<- ifelse((B$ColB1 %in% A$ColA1 | B$ColB1 %in% AColA2), "animal from ColA1" , NA)

这怎么会变短？通过应用apply函数，它会变得更快吗？

Answer 1

索引的使用也是选项：

i <- dfB$ColB1 %in% unlist(dfA)
dfB$ColB2[i] <- as.character(dfB$ColB2[i])

结果：

> dfB
  ColB1 ColB2
1  Lion  Lion
2   Cat    NA
3 Tiger Tiger
4   Dog   Dog

Answer 2

您可以尝试使用dplyr：

library(dplyr)

dfB %>%
  mutate(colB3 = if_else(ColB1 %in% unlist(dfA), ColB1, NULL))

给出：

   ColB1  ColB2  colB3
1   Lion   Lion   Lion
2    Cat     NA     NA
3  Tiger  Tiger  Tiger
4    Dog    Dog    Dog

输入：

 dput(dfA)
structure(list(ColA1 = structure(c(2L, 3L, 4L, 1L), .Label = c("Bat", 
"Dog", "Lion", "Zebra"), class = "factor"), ColA2 = structure(c(2L, 
1L, 4L, 3L), .Label = c("Dog", "Lion", "Parrot", "Tiger"), class = "factor")), class = "data.frame", row.names = c(NA, 
-4L), .Names = c("ColA1", "ColA2"))

dput(dfB)
structure(list(ColB1 = structure(c(3L, 1L, 4L, 2L), .Label = c("Cat", 
"Dog", "Lion", "Tiger"), class = "factor"), ColB2 = structure(c(2L, 
3L, 4L, 1L), .Label = c("Dog", "Lion", "NA", "Tiger"), class = "factor")), class = "data.frame", row.names = c(NA, 
-4L), .Names = c("ColB1", "ColB2"))

Answer 3

这可能是最简单的：

df_B$ColB2 <- ifelse(df_B$ColB1 %in% unlist(df_A[,c(1:2)]), df_B$ColB1, NA)

输出：

  ColB1 ColB2
1  Lion  Lion
2   Cat  <NA>
3 Tiger Tiger
4   Dog   Dog

要在df_A的每列中找到与df_B $ ColB1中的值匹配的单个索引，您可以使用以下内容：

x<-apply(df_A[,c(1:2)],2,function(x) sapply(df_B$ColB1, function(i) grep(i,x)))

str（x）的输出：

List of 2
$ ColA1:List of 4
 ..$ Lion : int 2
 ..$ Cat  : int(0) 
 ..$ Tiger: int(0) 
 ..$ Dog  : int 1
$ ColA2:List of 4
 ..$ Lion : int 1
 ..$ Cat  : int(0) 
 ..$ Tiger: int 3
 ..$ Dog  : int 2

ifelse函数接受if语句的输出作为返回的向量

3 个答案: