替换NA值

问题描述：

我有一个具有三个值的变量，NA，是，MayBe.

I have a variable that has three values, NA, Yes, MayBe.

当我在该变量上使用级别和类函数时，我会得到这些值

When I use levels and class function on that variable I get theses values

          > levels(Data1$Case)
          "Yes"                 "May Be"

          > class(Data1$Case)
          "factor"

我正在尝试将NA值替换为否，所以我使用此代码

I am trying to replace the NA values with No so I use this code

     Data1$Col1[is.na(Data1$Col1)]= "No"

我遇到错误

       In `[<-.factor`(`*tmp*`, is.na(Data1$Col1), value = c(NA,  :
       invalid factor level, NA generated

我写了一个ifelse语句来替换NA，

I wrote an ifelse statement to replace the NA,

      Data1$Col1=ifelse(is.na(Data1$Col1_ == 'TRUE'), "No",Data1$Col1)

这可行，但是我正在寻找一些有效的方法来替换NA.

and this works but I am looking for some efficient ways to do replace the NAs.

答

您可以使用addNA()和levels<-替换功能.

You can use addNA() and the levels<- replacement function.

x <- factor(c(NA, "Yes", "Maybe"))
# [1] <NA>  Yes   Maybe
# Levels: Maybe Yes

## If present, add NA to the factor levels
addNA(x)
# [1] <NA>  Yes   Maybe
# Levels: Maybe Yes <NA>
y <- addNA(x)

## replace the NA level with 'No'
levels(y)[is.na(levels(y))] <- "No"
y
# [1] No    Yes   Maybe
# Levels: Maybe Yes No

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