如何在R循环中将变量列表视为数据框列名而非字符串？

原代码问题分析 #

• 核心错误：直接将列名字符串传入grepl，而非列的实际数据。cod_acme_raw_vars[[i]]是列名（如"ucod"），不是deaths16_21中该列的数值，导致grepl一直在检查枪械代码是否出现在列名里，而非列内容中。
• 结果覆盖问题：每次循环都会重写all_firearm列，最终仅保留最后一次循环的检查结果，无法累积所有列的匹配情况。

方案1：高效正则匹配（推荐） #

通过将firearm_char合并为单个正则表达式，一次性检查所有枪械代码，再遍历各列累积匹配结果：

cod_acme_raw_vars <- c("ucod","acme1","acme2","acme3","acme4","acme5","acme6","acme7","acme8","acme9","acme10","acme11")
firearm_char <- c("W32","W33","W34","X72","X73","X74","X93","X94","X95","Y22","Y23","Y24","Y350","U014")

# 初始化all_firearm为全FALSE
deaths16_21$all_firearm <- FALSE

# 合并枪械代码为正则模式（|分隔表示匹配任意一个）
firearm_pattern <- paste(firearm_char, collapse = "|")

# 遍历每个目标列
for (col_name in cod_acme_raw_vars) {
  # 获取当前列的实际数据
  col_data <- deaths16_21[[col_name]]
  # 检查当前列中是否有任意枪械代码匹配
  current_matches <- grepl(firearm_pattern, col_data)
  # 累积匹配结果：只要任意列匹配，该行设为TRUE
  deaths16_21$all_firearm <- deaths16_21$all_firearm | current_matches
}

方案2：修正嵌套循环 #

如果坚持使用嵌套循环，需修正列数据的获取方式，并通过逻辑或操作累积结果：

cod_acme_raw_vars <- c("ucod","acme1","acme2","acme3","acme4","acme5","acme6","acme7","acme8","acme9","acme10","acme11")
firearm_char <- c("W32","W33","W34","X72","X73","X74","X93","X94","X95","Y22","Y23","Y24","Y350","U014")

# 初始化all_firearm为全FALSE
deaths16_21$all_firearm <- FALSE

for (i in seq_along(cod_acme_raw_vars)) {
  # 关键：用[[获取列的实际数据，而非列名字符串
  col_data <- deaths16_21[[cod_acme_raw_vars[i]]]
  
  for (j in seq_along(firearm_char)) {
    # 检查当前枪械代码是否在当前列的行中
    current_matches <- grepl(firearm_char[j], col_data)
    # 累积结果：保留所有匹配情况
    deaths16_21$all_firearm <- deaths16_21$all_firearm | current_matches
  }
}

关键要点 #

• 使用deaths16_21[[col_name]]获取列的实际数据，而非直接使用列名字符串。
• 通过|逻辑或操作累积匹配结果，确保只要任意列、任意枪械代码匹配，该行的all_firearm就为TRUE。

内容的提问来源于stack exchange，提问作者rojopomme