根据R中的字符值创建新列

Question

我有一个名为“full_name”的专栏，它展示了两支球队，例如：“曼联赢利物浦”、“利物浦赢曼联”、“切尔西赢阿森纳赢”等等。

我希望能够把球队区分为北和南，如果“曼联赢利物浦赢”或者“利物浦赢曼联赢U赢”，那么这将被编码为“北方”，而如果“切尔西赢阿森纳赢了”，这是编码为“南方”等等。

levels(raw_data$full_name)[levels(raw_data$full_name)== "Man U to win Liverpool to win"] <- 'North'
levels(raw_data$full_name)[levels(raw_data$full_name)== "Liverpool to win Man U to win"] <- 'North'
levels(raw_data$full_name)[levels(raw_data$full_name)== "Chelsea to win Arsenal to win"] <- 'South'

上面的代码不会产生任何错误，但是dataframe保持不变，并且没有产生所需的输出。是做这个的方法吗？

Answer 1

这里有一个可以帮助您的tidyverse方法的示例。

library(dplyr)

north <- c("Man U to win Liverpool to win","Liverpool to win Man U to win")
south <- c("Chelsea to win Arsenal to win")


df <- 
  data.frame(full_name = sample(c(north,south),size = 5,replace = TRUE))
             
df %>% 
  mutate(region = case_when(
    full_name %in% north ~ "North",
    full_name %in% south ~ "South"
  ))

                      full_name region
1 Chelsea to win Arsenal to win  South
2 Man U to win Liverpool to win  North
3 Chelsea to win Arsenal to win  South
4 Man U to win Liverpool to win  North
5 Man U to win Liverpool to win  North

Answer 2

下面是fct_recode的一个选项

library(forcats)
raw_data$full_name <- with(raw_data, fct_recode(full_name, 
   North =  "Man U to win Liverpool to win",
   North = "Liverpool to win Man U to win",
   South  =  "Chelsea to win Arsenal to win"))

或者使用base R

factor(raw_data$full_name, levels = c("Chelsea to win Arsenal to win", 
"Liverpool to win Man U to win", "Man U to win Liverpool to win"
), labels = c("South", "North", "North"))

或者如果我们想使用levels

lvls_to_change <-  c("Man U to win Liverpool to win",
   "Liverpool to win Man U to win", "Chelsea to win Arsenal to win")
lvsl_new <- c("North", "North", "South")
i1 <- levels(raw_data$full_name) %in% lvls_to_change
levels(raw_data$full_name)[i1] <- lvsl_new[match(levels(raw_data$full_name)[i1], lvls_to_change)]

数据

raw_data <- structure(list(full_name = structure(c(2L, 2L, 3L, 2L,
 1L), levels = c("Chelsea to win Arsenal to win", 
"Liverpool to win Man U to win", "Man U to win Liverpool to win"
), class = "factor")), row.names = c(NA, -5L), class = "data.frame")

Answer 3

以下是另一种方法：

library(dplyr)
library(stringr)

north <- c("Liverpool|Man")
south <- c("Chelsea|Arsenal")

df %>% 
  mutate(region = case_when(str_detect(full_name, north) ~ "North",
                            str_detect(full_name, south) ~ "South",
                            TRUE ~ NA_character_))

                      full_name region
1 Liverpool to win Man U to win  North
2 Chelsea to win Arsenal to win  South
3 Man U to win Liverpool to win  North
4 Chelsea to win Arsenal to win  South
5 Liverpool to win Man U to win  North