r - 如何解码包含 R 中另一列文本的列？

Question

我有一个数据框，在答案列中包含编码的调查答案，键作为字符列中的一个字符串:

df <- data.frame(answer = c(1, 2, 1, 3, 1),
                 key = c("1 = Answer One 2 = Answer Two 3 = Answer Three", "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI", 
                         "1 = Answer abc 2 = Answer def 3 = Answer ghi", "1 = Answer One 2 = Answer Two 3 = Answer Three",
                         "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI"))

print(df)

  answer                                            key
1      1 "1 = Answer One 2 = Answer Two 3 = Answer Three"
2      2   "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI"
3      1   "1 = Answer abc 2 = Answer def 3 = Answer ghi"
4      3 "1 = Answer One 2 = Answer Two 3 = Answer Three"
5      1   "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI"

如何使用键列中的数据对答案列进行解码，以便获得此结果？

df_result <- data.frame(answer = c(1, 2, 1, 3, 1),
                 key = c("1 = Answer One 2 = Answer Two 3 = Answer Three", "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI", 
                         "1 = Answer abc 2 = Answer def 3 = Answer ghi", "1 = Answer One 2 = Answer Two 3 = Answer Three",
                         "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI"),
                 answer_decoded = c("Answer One", "Answer DEF", "Answer abc", "Answer Three","Answer ABC"))

print(df_result)

  answer                                            key answer_decoded
1      1 "1 = Answer One 2 = Answer Two 3 = Answer Three"     "Answer One"
2      2   "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI"     "Answer DEF"
3      1   "1 = Answer abc 2 = Answer def 3 = Answer ghi"     "Answer abc"
4      3 "1 = Answer One 2 = Answer Two 3 = Answer Three"   "Answer Three"
5      1   "1 = Answer ABC 2 = Answer DEF 3 = Answer GHI"     "Answer ABC"

我无法使用因子标签，因为我有太多不同的项目无法手动创建它们。

Answer 1

我们可以根据“answer”值提取子字符串 - 使用 str_c 创建要提取的模式，即粘贴带有空格的“answer”，后跟 =和一个或多个非数字字符 (\\D+) 并删除前缀部分，包括 = 和带有 trimws

library(stringr)
library(dplyr)
df %>%
   mutate(answer_decoded = trimws(str_extract(key, 
        str_c(answer, ' = \\D+')), whitespace = ".*=\\s+|\\s+"))

-输出

  answer                                            key answer_decoded
1      1 1 = Answer One 2 = Answer Two 3 = Answer Three     Answer One
2      2   1 = Answer ABC 2 = Answer DEF 3 = Answer GHI     Answer DEF
3      1   1 = Answer abc 2 = Answer def 3 = Answer ghi     Answer abc
4      3 1 = Answer One 2 = Answer Two 3 = Answer Three   Answer Three
5      1   1 = Answer ABC 2 = Answer DEF 3 = Answer GHI     Answer ABC