将缺失的值替换为另一列中的值 [英] Replace missing values with a value from another column

问题描述

如果我有

s <- data.frame(ID=c(191, 282, 202, 210), Group=c("", "A", "", "B"), stringsAsFactors=FALSE)
s
   ID Group
1 191      
2 282     A
3 202      
4 210     B

我可以这样用N替换空单元格:

I can replace the empty cells with N like this:

ds$Group[ds$Group==""]<-"N"

s
   ID Group
1 191     N 
2 282     A
3 202     N
4 210     B

但是我需要用另一列中的值替换空单元格.我该怎么做?:

But I would need to replace the empty cells with a value from another column. How can I accomplish this?:

s
   ID Group Group2
1 191     D      D
2 282     A      G
3 202     G      G
4 210     B      D

推荐答案

ifelse(test, yes, no)是一个方便的功能，它可以在矢量上使用.使用最后一个data.frame:

ifelse(test, yes, no) is a handy function to do just that, and it can be used on vectors. Using your last data.frame:

s <- data.frame(ID = c(191, 282, 202, 210),
    Group = c("", "A", "", "B"),
    Group2 = c("D", "G", "G", "D"))

s$Group <- ifelse(test = s$Group != "", yes = s$Group, no = s$Group2)

第一个参数是测试.对于向量中的每个值，如果test为true，则它将采用yes中的值，否则将采用no中的值.

The first argument is the test. For each value in the vector, if the test is true, then it will take the value in yes, otherwise it will take the value in no.

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