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我试图在数据框中设置一个等于“美国”或“外国”的列，具体取决于国家/地区。我相信这样做的正确方法是编写一个函数，然后用于sapply实际更新数据帧。这是我第一次在 in 中尝试这样的事情R，SQL我会写一个UPDATE查询。

这是我的数据框：

str(clients)
'data.frame':   252774 obs. of  4 variables:
 $ ClientID     : Factor w/ 252774 levels "58187855","59210128",..: 19 20 21 22 23 24 25 26 27 28 ...
 $ Country          : Factor w/ 207 levels "Afghanistan",..: 196 60 139 196 196 40 40 196 196 196 ...
 $ CountryType     : chr  "" "" "" "" ...
 $ OrderSize        : num  12.95 21.99 5.00 7.50 44.5 ...


head(clients)
       ClientID  Country       CountryType  OrderSize
1      58187855  United States              12.95
2      59210128  France                     21.99
3      65729284  Pakistan                   5.00
4      25819711  United States              7.50
5      62837458  United States              44.55
6      88379852  China                      99.28

我试图编写的函数是这样的：

updateCountry <- function(x) {
  if (clients$Country == "US") {
        clients$CountryType <- "US"
  } else {
    clients$CountryType <- "Foreign"
    }
}

然后我会像这样应用它：

sapply(clients, updateCountry)

当我sapply在数据框的头部运行时，我得到了这个：

"US" "US" "US" "US" "US" "US" 
Warning messages:
1: In if (clients$Country == "United States") { :
  the condition has length > 1 and only the first element will be used
2: In if (clients$Country == "United States") { :
  the condition has length > 1 and only the first element will be used
3: In if (clients$Country == "United States") { :
  the condition has length > 1 and only the first element will be used
4: In if (clients$Country == "United States") { :
  the condition has length > 1 and only the first element will be used
5: In if (clients$Country == "United States") { :
  the condition has length > 1 and only the first element will be used
6: In if (clients$Country == "United States") { :
  the condition has length > 1 and only the first element will be used

该函数似乎正确地对 Country 进行了分类，但没有正确更新 clients$CountryType 列。我究竟做错了什么？另外-这是完成更新数据框的最佳方法吗？

4

1 回答 1

5

ifelse看起来就像你在这里真正想要的。它是 if/else 构造的矢量化版本。

 clients$CountryType <- ifelse(clients$Country == "US", "US", "Foreign")
于 2012-10-05T15:18:12.443 回答