Question

我是R的初学者并且有问题。真的很感激任何帮助！当我在以下（简化）的情况下应用for循环时，我收到一条错误消息，说“替换有5行，数据有4”

Country <- c("Germany", "France", "Italy", "Spain")
Unemploy <- c(2, 3, 4, 10)
Growth <- c(2, 7, 6, 9)
data <- data.frame(Country, Unemploy, Growth)

for (i in data$Country) {
     if (identical(data$Country[i], "France")) {
          data$Growth[i] <- "5"
     } else {
          data$Growth[i] <- "2"
     }
}

发出以下信息：

Error in `$<-.data.frame`(`*tmp*`, "Growth", value = c("2", "2", "2",  : 
replacement has 5 rows, data has 4

Answer 1

使用ifelse代替

data[ ,"Growth"] <- ifelse(data[ , "Country"] == "France", "5", "2")

Answer 2

检查出来：

> for (i in data$Country){print(i)}
[1] "Germany"
[1] "France"
[1] "Italy"
[1] "Spain"

i in data$Country语法遍历该data.frame属性中的值。然后，您使用i，就好像它是一个数字索引。所以你要做的就是这样：

for (i in 1:length(data$Country)) {if (identical(data$Country[i],"France"))
+ {data$Growth[i]<-"5"}else{data$Growth[i]<-"2"}}

如上所述，上述内容并非惯用R，请参阅@ Jilber的答案以获得更为惯用的解决方案。

Answer 3

尝试：

for (i in 1:length(data$Country)) {
    ...

For循环：替换比数据多一行

3 个答案: