在R语言中根据Case_ID条件为字符串变量添加指定子串

需求说明 #

根据Case_ID和Question的组合，给Question字符串末尾添加对应相关性标识：

• 当Case_ID为1234时：QS1拼接"02"，QS2、QS3拼接"00"
• 当Case_ID为4321时：QS1拼接"00"，QS2拼接"01"，QS3拼接"02"

输入数据构造 #

先构造示例输入数据：

# 构造输入数据框
input_df <- data.frame(
  Case_ID = c(1234, 4321, 1234, 1234, 4321, 4321),
  Question = c("QS1", "QS1", "QS3", "QS2", "QS3", "QS2"),
  stringsAsFactors = FALSE
)

实现方法 #

方法1：使用dplyr包（逻辑清晰，推荐） #

加载dplyr包后，用case_when定义多条件规则，再通过paste0拼接字符串：

library(dplyr)

output_df <- input_df %>%
  mutate(
    Question = paste0(
      Question,
      case_when(
        Case_ID == 1234 & Question == "QS1" ~ "02",
        Case_ID == 1234 & (Question == "QS2" | Question == "QS3") ~ "00",
        Case_ID == 4321 & Question == "QS1" ~ "00",
        Case_ID == 4321 & Question == "QS2" ~ "01",
        Case_ID == 4321 & Question == "QS3" ~ "02"
      )
    )
  )

方法2：基础R实现（无需额外包） #

用嵌套ifelse完成条件判断，搭配paste0拼接字符串：

output_df <- input_df
output_df$Question <- paste0(
  output_df$Question,
  ifelse(output_df$Case_ID == 1234,
         ifelse(output_df$Question == "QS1", "02", "00"),
         ifelse(output_df$Question == "QS1", "00",
                ifelse(output_df$Question == "QS2", "01", "02"))
  )
)

输出结果 #

运行上述代码后，得到的输出数据如下：

内容的提问来源于stack exchange，提问作者C K