無法將NA放入數據集的空列

Question

我正在使用泰坦尼克號dataset。在大多數行中，屬性Cabin爲空。所以，我想用NA替換所有那些有Cabin列的空值的行。

要做到這一點，我寫道：

train[train$Cabin==" "] <- "NA"

write.csv(train,file="editedtrain.csv") 

但文件editedtrain.csv不具有具有Cabin列空值的行NA。

以下是運行上述代碼後head(train)的結果。

  Ticket   Fare  Cabin Embarked 
1  A/5 21171   7.2500    S 
2   PC 17599   71.2833 C85  C 
3  STON/O2.3101282  7.9250    S 
4   113803   53.1000 C123  S 
5   373450   8.0500    S 
6   330877   8.4583    Q 

而且dput：

structure(
    list(
    PassengerId = 1:6, 
    Survived = c(0L, 1L, 1L, 1L,0L, 0L), 
    Pclass = c(3L, 1L, 3L, 1L, 3L, 3L), 
    Name = c("Braund, Mr. Owen Harris", "Cumings, Mrs. John Bradley (Florence Briggs Thayer)", "Heikkinen, Miss. Laina", "Futrelle, Mrs. Jacques Heath (Lily May Peel)", "Allen, Mr. William Henry", "Moran, Mr. James"), 
    Sex = c("male", "female", "female", "female", "male", "male"), 
    Age = c(22, 38, 26, 35, 35, NA), 
    SibSp = c(1L, 1L, 0L, 1L, 0L, 0L), 
    Parch = c(0L, 0L, 0L, 0L, 0L, 0L), 
    Ticket = c("A/5 21171", "PC 17599", "STON/O2. 3101282", "113803", "373450", "330877"), 
    Fare = c(7.25, 71.2833, 7.925, 53.1, 8.05, 8.4583), 
    Cabin = c("", "C85", "", "C123", "", ""), 
    Embarked = c("S", "C", "S", "S", "S", "Q")), 
    .Names = c("PassengerId", "Survived", "Pclass", "Name", "Sex", "Age", "SibSp", "Parch", "Ticket", "Fare", "Cabin", "Embarked"), 
    row.names = c(NA, 6L), class = "data.frame") 

如何實現我想要什麼？

Answer 1

正如您在dput中看到的，train$Cabin缺失值是""。

因此，要將其更改爲NA，您不能將空格放在引號內。

你只需要做到這一點train$Cabin[train$Cabin==""] <- NA

您需要指定您希望Cabin列被改變，而r識別NA不帶引號。

---

由於Frank評論說，如果你只是用na.strings = ""閱讀.csv文件，它會自動完成這項工作。這將是這樣的：

train <- read.csv("YOUR_PATH\\train.csv", stringAsFactors = F, na.strings = "") 

---

一些提示：

• 當你read.csv()，設置stringsAsFactors = F，如果你希望你的角色列，繼續爲字符，而不是因素

• 當你write.csv()，設置row.names = F如果你不想它創建一個行ID爲的列。