Question

对于以下数据表，如果列水果包含“ apple”或“ orange”，我想重命名列水果，即，我想在DT中而不是DT2中重命名列水果。

library(data.table)
DT <- data.table(colour = c("green", "red", "red", "red", "blue","red"), fruit = c("apple", "orange", "pear", "apple", "apple","banana"))
DT2 <- data.table(colour = c("green", "red", "red", "red", "blue","red"), fruit = c("pear", "pear", "pear", "banana", "pear","banana"))

我想先搜索数据表中是否包含水果列，所以我尝试了下面的代码，但是它在DT和DT2中重命名了水果：

alist <- list(DT, DT2)
lapply(alist, function(x) {
if ("fruit" %in%  colnames(x)){
x <- x[fruit=="apple"|fruit=="orange", setnames(x, old="fruit", new="appfruit")]
x}})

任何帮助将不胜感激。

Answer 1

将功能更改为：

lapply(alist, function(x) {
  if(any(x[["fruit"]] %in% c("apple","orange"))) {
    setnames(x, old = "fruit", new = "appfruit")
  }}
)

将给出预期的结果（有关扩展的示例数据，请参见下文）：

> alist
[[1]]
   colour appfruit
1:  green    apple
2:    red   orange
3:    red     pear
4:    red    apple
5:   blue    apple
6:    red   banana

[[2]]
   colour  fruit
1:  green   pear
2:    red   pear
3:    red   pear
4:    red banana
5:   blue   pear
6:    red banana

[[3]]
   colour veggie
1:  green  apple
2:    red   pear
3:    red   pear
4:    red banana
5:   blue   pear
6:    red banana

如您所见，当没有fruit列时，列名不会更改。

使用的数据：

DT1 <- data.table(colour = c("green", "red", "red", "red", "blue","red"), fruit = c("apple", "orange", "pear", "apple", "apple","banana"))
DT2 <- data.table(colour = c("green", "red", "red", "red", "blue","red"), fruit = c("pear", "pear", "pear", "banana", "pear","banana"))
DT3 <- data.table(colour = c("green", "red", "red", "red", "blue","red"), veggie = c("apple", "pear", "pear", "banana", "pear","banana"))

alist <- list(DT1, DT2, DT3)

根据行值更改列名

1 个答案: