R-在一个数据帧中组合两列，创建新的列标题，使用lappy和merge在大型数据集上重复

我是一个新手R用户，我有一个大数据框（1700列），它由数据和标志列组成：

df <- data.frame( "100249 MERCURY TOTAL ug/L" = runif(10),
              "100397 TRIHALOMETHANES ug/L" = runif(10),
              "100397 TRIHALOMETHANES ug/L FLAG" = c("L", "L", NA, "L", "L", NA, "L", NA, NA, NA),
              "100407 XYLENE ug/L" = runif(10),
              "100407 XYLENE ug/L FLAG" = c("L", NA, "L", "L", "L", NA, "L", NA, "L", "L"), 
              check.names=FALSE ) 

非常感谢您的建议。

Reduce（f=函数（dat，col）{
Reduce(f = function(dat, col) {
  x <- sub(" ?FLAG$", "", col)
  if (!x %in% names(dat)) return(dat)
  dat[paste0(x, "_COMB")] <- paste(dat[[col]], dat[[x]])
  dat[c(col, x)] <- NULL
  dat
}, x = grep("FLAG$", names(df), value = TRUE), init = df)

#    100249 MERCURY TOTAL ug/L 100397 TRIHALOMETHANES ug/L_COMB 100407 XYLENE ug/L_COMB
# 1                 0.04353999              L 0.375519647961482      L 0.95818781433627
# 2                 0.49308933              L 0.931443430483341    NA 0.744603316066787
# 3                 0.68270299             NA 0.409499574452639     L 0.993966163368896
# 4                 0.26546071             L 0.0351015995256603     L 0.696171462768689
# 5                 0.95956891              L 0.603019695729017     L 0.709421107778326
# 6                 0.01842927              NA 0.96781362616457    NA 0.201458259951323
# 7                 0.12114176              L 0.734256325522438     L 0.457969205919653
# 8                 0.93771709             NA 0.309347201371565    NA 0.508297981694341
# 9                 0.47122685             NA 0.822285959031433      L 0.87013426842168
# 10                0.11501974              NA 0.56137450854294     L 0.153437153436244

x请显示（不告诉）所需的输出。谢谢，这对我的数据子集有效！但是当我在整个数据集上运行时，我得到了以下错误：`error in
[@MKruk我已经编辑了我的答案（在“FLAG”之前删除了一个空格），你能再试一次吗？通过这次最新的编辑，它没有合并列，只是删除了“FLAG”标签并用“\u COMB”替换它在“标志”列中。一旦我将数据子集以从数据集中排除ID变量，我就让您的初始脚本开始工作。如果您将其编辑回原始脚本，我将向上投票。谢谢！
Reduce(f = function(dat, col) {
  x <- sub(" ?FLAG$", "", col)
  if (!x %in% names(dat)) return(dat)
  dat[paste0(x, "_COMB")] <- paste(dat[[col]], dat[[x]])
  dat[c(col, x)] <- NULL
  dat
}, x = grep("FLAG$", names(df), value = TRUE), init = df)

#    100249 MERCURY TOTAL ug/L 100397 TRIHALOMETHANES ug/L_COMB 100407 XYLENE ug/L_COMB
# 1                 0.04353999              L 0.375519647961482      L 0.95818781433627
# 2                 0.49308933              L 0.931443430483341    NA 0.744603316066787
# 3                 0.68270299             NA 0.409499574452639     L 0.993966163368896
# 4                 0.26546071             L 0.0351015995256603     L 0.696171462768689
# 5                 0.95956891              L 0.603019695729017     L 0.709421107778326
# 6                 0.01842927              NA 0.96781362616457    NA 0.201458259951323
# 7                 0.12114176              L 0.734256325522438     L 0.457969205919653
# 8                 0.93771709             NA 0.309347201371565    NA 0.508297981694341
# 9                 0.47122685             NA 0.822285959031433      L 0.87013426842168
# 10                0.11501974              NA 0.56137450854294     L 0.153437153436244

dat <- df
for (col in grep("FLAG$", names(df), value = TRUE)) {
  x <- sub(" ?FLAG$", "", col)
  if (!x %in% names(dat)) next
  dat[paste0(x, "_COMB")] <- paste(dat[[col]], dat[[x]])
  dat[c(col, x)] <- NULL
}
dat