在dplyr的case_when()中实现条件值替换的问题与解决

问题背景 #

有一组亲子对应关系数据集：

key <- data.frame(parent = c("ID1", "ID2", "ID3"), infant = c("ID4", "ID5", "ID6"))

另有一个行为数据集，其中用通用代码inf指代当前亲代对应的子代，亲代ID存储在id列：

df <- data.frame(time_point = 1:6, id = rep("ID2", 6), social1 = c(NA, NA, "inf", NA, NA, NA), social2 = c(NA, NA, NA, NA, NA, "inf"), social3 = c("inf", NA, NA, NA, NA, NA))

需求是将df中所有inf替换为key里对应亲代的子代ID。

初始尝试与报错 #

尝试用mutate+case_when实现替换时出现报错：

df %>% 
  mutate(social1 = case_when(
    grepl("inf", social1) ~ key[key$parent == id,]$infant,
    TRUE ~ social1
  ))

报错信息：

Error in mutate():
ℹ In argument: social1 = case_when(...).
Caused by error in case_when():
! Can't recycle ..1 (left) (size 6) to match ..1 (right) (size 2).

问题核心是在case_when的替换逻辑中引用其他列时，出现了向量长度不匹配的回收问题。

复杂场景更新 #

实际场景更复杂，inf可能与其他ID出现在同一字符串中：
更新后的数据集：

key <- data.frame(parent = c("ID1", "ID2", "ID3"), infant = c("ID4", "ID5", "ID6"))

df <- data.frame(time_point = 1:6, id = rep("ID2", 6), social1 = c(NA, NA, "inf ID7", NA, NA, NA), social2 = c(NA, NA, NA, NA, NA, "inf"), social3 = c("ID8 inf", NA, NA, NA, NA, NA))

尝试通过left_join关联亲子表后用gsub替换，出现警告：

df %>% 
  left_join(., key, by = c("id" = "parent")) %>%
  mutate(social1 = case_when(
    grepl("inf", social1) ~ gsub("inf",infant, social1),
    TRUE ~ social1
  ))

警告信息：

Warning message:
There was 1 warning in mutate().
ℹ In argument: social1 = case_when(...).
Caused by warning in gsub():
! argument 'replacement' has length > 1 and only the first element will be used

最终解决方案 #

在mutate前调用rowwise()，按行处理即可解决该问题，完整代码如下：

df %>% 
  left_join(., key, by = c("id" = "parent")) %>%
  rowwise() %>%
  mutate(
    social1 = case_when(
      grepl("inf", social1) ~ gsub("inf", infant, social1),
      TRUE ~ social1
    ),
    social2 = case_when(
      grepl("inf", social2) ~ gsub("inf", infant, social2),
      TRUE ~ social2
    ),
    social3 = case_when(
      grepl("inf", social3) ~ gsub("inf", infant, social3),
      TRUE ~ social3
    )
  ) %>%
  ungroup() # 处理完取消按行分组，避免后续操作受影响

该方法虽因逐行处理速度较慢，但能有效解决向量长度不匹配的问题，完成字符串中inf的替换。

内容的提问来源于stack exchange，提问作者gavago