r - 根据另一列更改一列的值(对于某些行)

Question

我有一个数据框 df

ID <- c(1,2,3,4,5)
category <- c("Shirts", "Shirts", "Shirts", "Sweaters", "Sweaters")
subcategory <- c("V-Neck","V-Neck","Round","Striped","Striped")
df <- data.frame(ID,category,subcategory)

ID  category   subcategory
1   Shirts     V-Neck
2   Shirts     V-Neck
3   Shirts     Round
4   Sweaters   Striped
5   Sweaters   Striped

我想将“子类别”列的名称分配给所有行的“类别”列，其中类别 ==“衬衫”

我的结果应该是这样的:

ID  category   subcategory
1   V-Neck     V-Neck
2   V-Neck     V-Neck
3   Round      Round
4   Sweaters   Striped
5   Sweaters   Striped

我试过了

library(dplyr)
res <- df %>% 
  filter(category=="Shirts") %>% 
  mutate(category=subcategory)

结果与我正在寻找的结果接近，但它不包含第 4 行和第 5 行。

有人可以帮我解决这个问题吗？

Answer 1

不确定您是否正在寻找仅“dplyr”的答案(您的问题没有被标记为这样)，但这对于“data.table”来说非常简单:

library(data.table)
as.data.table(df)[category == "Shirts", category := subcategory][]
#    ID category subcategory
# 1:  1        V           V
# 2:  2        V           V
# 3:  3    Round       Round
# 4:  4 Sweaters     Striped
# 5:  5 Sweaters     Striped

我想用“dplyr”，你可以试试ifelse(也可能是replace):

df[-1] <- lapply(df[-1], as.character)  ## Convert factors to characters
df %>%
  mutate(category = ifelse(category == "Shirts", 
                           subcategory, category))