Question

我有一个数据帧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

我想将列“subategory”的名称分配给所有行的“category”列，其中category ==“Shirts”

我的结果应如下所示：

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

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

并且结果接近我要查找的内容，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＆＃34; dplyr＆＃34;只回答（你的问题没有标记为这样）但这对于＆＃34; data.table＆＃34;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＆＃34; dplyr＆＃34;，你可以尝试ifelse（可能还有replace）：

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

Answer 2

我知道它可能很长一段时间（并且远不如Amanda Mahto的解决方案那么优雅）但您可以将类别和子类别列转换为字符，进行索引和更新，然后转换他们回到了一个因素。

df$category <- as.character(df$category); df$subcategory <- as.character(df$subcategory)
indx <- category == "Shirts" ; df$category[indx] <- df$subcategory[indx]
df$category <- as.factor(df$category); df$subcategory <- as.factor(df$subcategory)

Answer 3

df$category <- ifelse(df$category=="Shirts",
                      as.character(df$subcategory),
                      as.character(df$category)) 
df
#   ID category subcategory
# 1  1        V           V
# 2  2        V           V
# 3  3    Round       Round
# 4  4 Sweaters     Striped
# 5  5 Sweaters     Striped

根据另一列（对于某些行）更改列的值

3 个答案: