根据另一列更改列值，但仅适用于第一列和第二列 (R) 中的某些条件

Question

我有一个数据框。

city <- as.character(c("London", "Unknown", "Birmingham", "Bristol", "Unknown", "Unknown", "Unknown", "Unknown"))
city_details <- as.character(c("London", "Camden", "Birmingham", "Outside London", "Camden Town", "Westminster", "London", "Birmingham"))
city_data <- data.frame(city, city_details)

虽然城市列中的一些值是未知的，但查看 city_details 会发现其中大部分实际上都在伦敦。

所以，我可以替换其中的一些：

city_data$city[grepl("Camden|Westminster", city_data$city_details)] <- 'London'

不过，city_details里面写着"London"的比较难，因为还有"Outside London"，所以我不想只拿起任何有 "London" 模式的东西。

出于此目的，我并不是在寻找一种只包含完全匹配的方法（因为这不太适合我的真实数据）。

所以我想做的只是对未知的城市值执行此替换。

目前我已经尝试了以下操作，但显然逻辑不对，因为它实际上所做的只是将城市列中的所有未知值更改为伦敦。

city_data <- within(city_data, city[city == "Unknown"] <- (city[grepl("London", city_details)] <- 'London'))

有人能帮忙吗？

Answer 1

我假设您只想在 city 未知且 city_details 提到 "London" 时替换城市名称。在这种情况下，您可以使用以下内容：

city_data$city[(as.numeric(grepl("Unknown", city)) + as.numeric(grepl("London", city_details))) == 2] <- "London"

这是否回答了您的问题？

Answer 2

我建议如下：

one_hot <- grepl("Camden|Westminster|London", city_data$city_details) &
  city_data$city == "Unknown"
city_data$city[one_hot] <- "London"

示例：

city <- as.character(c("London", "Unknown", "Birmingham", "Bristol", "Unknown", "Unknown", "Unknown", "Unknown"))
city_details <- as.character(c("London", "Camden", "Birmingham", "Outside London", "Camden Town", "Westminster", "London", "Tottenham"))
city_data <- data.frame(city, city_details)

> city_data
        city   city_details
1     London         London
2    Unknown         Camden
3 Birmingham     Birmingham
4    Bristol Outside London
5    Unknown    Camden Town
6    Unknown    Westminster
7    Unknown         London
8    Unknown      Tottenham

> one_hot <- grepl("Camden|Westminster|London", city_data$city_details) &
+   city_data$city == "Unknown"
> city_data$city[one_hot] <- "London"
> city_data
        city   city_details
1     London         London
2     London         Camden
3 Birmingham     Birmingham
4    Bristol Outside London
5     London    Camden Town
6     London    Westminster
7     London         London
8    Unknown      Tottenham

Answer 3

我还想出了下面的方法，对我来说似乎更简洁、更直观。无需转换为数字。

city_data$city[grepl("Unknown", city_data$city) & 
               grepl("London|Camden|Westminster", city_data$city_details)] <- "London"

根据另一列更改列值，但仅适用于第一列和第二列 (R) 中的某些条件

Change column value based on another column, but only for certain conditions in the first AND second column (R)

r

dataframe

grepl