如果在单独的列中满足条件，则重命名因子变量

问题描述

我有一个如下所示的df：

I have a df that looks like this:

df <- data.frame(
    A = sample(c("Dog", "Cat", "Cat", "Dog", "Fish", "Fish")),
    B = sample(c("Brown", "Black", "Brown", "Black", "Brown", "Black")))
df

   A      B
1  Dog    Brown
2  Cat    Black
3  Cat    Brown
4  Dog    Black
5  Fish   Brown
6  Fish   Black

当第二列满足条件Brown时，我想将因子变量Fish更改为Dog。

I want to rename (with dplyr, preferably) the factor variable "Fish" to "Dog" whenever the condition "Brown" is satisfied in the second column.

   A      B
1  Dog    Brown
2  Cat    Black
3  Cat    Brown
4  Dog    Black
5  Dog    Brown  #rename here
6  Fish   Black

推荐答案

您可以使用替换：

df %>% mutate(A = replace(A, which(A == "Fish" & B == "Brown"), "Dog"))
#     A     B
#1  Cat Black
#2 Fish Black
#3  Dog Black
#4  Dog Brown
#5  Cat Brown
#6  Dog Brown

这里有一个data.table版本：

And here's a data.table version:

library(data.table)
setDT(df)[A == "Fish" & B == "Brown", A := "Dog"]

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