R语言中循环生成条件列失败问题求助

在R语言中，我通过逐行代码可以基于partyid、vA至vH、E3019_A至E3019_H这些变量的条件，成功生成core_A至core_H共8列，但尝试用循环简化代码时出现报错，以下是相关代码和数据，需要找出循环代码的问题：

可正常运行的逐行代码 #

df1$core_A <- ifelse(df1$partyid == df1$vA, df1$E3019_A, NA)
df1$core_B <- ifelse(df1$partyid == df1$vB, df1$E3019_B, NA)
df1$core_C <- ifelse(df1$partyid == df1$vC, df1$E3019_C, NA)
df1$core_D <- ifelse(df1$partyid == df1$vD, df1$E3019_D, NA)
df1$core_E <- ifelse(df1$partyid == df1$vE, df1$E3019_E, NA)
df1$core_F <- ifelse(df1$partyid == df1$vF, df1$E3019_F, NA)
df1$core_G <- ifelse(df1$partyid == df1$vG, df1$E3019_G, NA)
df1$core_H <- ifelse(df1$partyid == df1$vH, df1$E3019_H, NA)

出错的循环代码 #

seq <- LETTERS[seq(1,8)]

for(i in seq){
  df1$core_[[i]] <- ifelse(df1$partyid == df1$v[[i]], df1$E3019_[[i]], NA)
}

简化后的样本数据 #

structure(list(E1004 = c("AUS_2019", "AUS_2019", "AUS_2019", 
"AUS_2019", "AUS_2019", "AUS_2019", "AUS_2019", "AUS_2019", "AUS_2019", 
"AUS_2019"), partyid = c(NA, NA, 36002, 36002, 36001, 36001, 
NA, NA, NA, 36001), vA = c(36001, 36001, 36001, 36001, 36001, 
36001, 36001, 36001, 36001, 36001), vB = c(36002, 36002, 36002, 
36002, 36002, 36002, 36002, 36002, 36002, 36002), vC = c(36003, 
36003, 36003, 36003, 36003, 36003, 36003, 36003, 36003, 36003
), E3019_A = c(10L, 7L, NA, 0L, NA, 6L, 8L, NA, 8L, 8L), E3019_B = c(4L, 
5L, NA, 9L, NA, 4L, 2L, 10L, 3L, 5L), E3019_C = c(2L, 3L, NA, 
5L, NA, 3L, 5L, NA, 6L, 0L)), row.names = c(NA, 10L), class = "data.frame")

问题分析与修正 #

循环代码的核心问题是列名的引用方式错误：

• df1$core_[[i]]、df1$v[[i]]、df1$E3019_[[i]]这种写法不符合R的语法，$运算符后不能直接跟[[i]]来拼接变量名，需要用字符串拼接生成完整列名，再通过[[ ]]运算符引用。

修正后的循环代码如下：

seq <- LETTERS[1:8]

for(i in seq){
  # 拼接完整列名
  core_col <- paste0("core_", i)
  v_col <- paste0("v", i)
  e_col <- paste0("E3019_", i)
  
  # 赋值操作
  df1[[core_col]] <- ifelse(df1$partyid == df1[[v_col]], df1[[e_col]], NA)
}

运行修正后的代码后，就能得到和逐行代码完全一致的结果。

内容的提问来源于stack exchange，提问作者Victor Shin