R语言循环生成缺失值哑变量报错求助（Stata转R新手）

Hey there! As someone making the switch from Stata to R, it's totally normal to hit small syntax snags—let's get your loop working correctly so you can generate those missing value dummy variables.

Why Your Current Code Throws Warnings #

Your warnings stem from two key syntax mistakes in how R handles dynamic column names:

1. reflex_working$i: R interprets this as a literal column named i, not the variable name stored in your loop iterator i. Since your data frame doesn't have a column called i, you get the "unknown column" warning.
2. reflex_working$miss_[i]: This syntax is invalid for creating dynamic column names. You need to combine the prefix miss_ with the original variable name to form the new column's proper name.

Corrected Loop Code #

Here's the fixed version of your loop that will generate the miss_变量名 columns exactly as you want:

varlist <- c("A7LECTUR", "A7GROASG", "A7RESPRJ", "A7WORPLC", "A7PRACTI", 
             "A7THEORI", "A7TEACHR", "A7PROBAL", "A7WRIASG", "A7ORALPR")

for (i in varlist) {
  # Create the new variable name by combining "miss_" with the original variable name
  new_var_name <- paste0("miss_", i)
  # Use [[ ]] to dynamically reference columns and assign the dummy variable
  reflex_working[[new_var_name]] <- ifelse(reflex_working[[i]] == -9, 1, 0)
}

How It Works #

• paste0("miss_", i) builds the exact new column name you need (e.g., miss_A7LECTUR when i is "A7LECTUR").
• reflex_working[[i]] tells R to pull the column whose name is stored in the variable i (instead of looking for a column literally named i).
• The ifelse() statement checks if the original value is -9 and assigns 1 if true, 0 otherwise—exactly matching your requirement.

Bonus: A Tidyverse Alternative (More Stata-like Syntax Feel) #

If you're open to using the dplyr package (part of the tidyverse, which has syntax that might feel more intuitive for Stata users), you can do this in one line without a loop:

library(dplyr)

reflex_working <- reflex_working %>%
  mutate(across(all_of(varlist), ~ifelse(.x == -9, 1, 0), .names = "miss_{.col}"))

• across(all_of(varlist)) tells R to apply the following operation to every variable in varlist.
• ~ifelse(.x == -9, 1, 0) is the operation: check each value ((.x) refers to the current variable) and assign the dummy value.
• .names = "miss_{.col}" automatically generates the new column names, replacing {.col} with the original variable name.

Both methods will produce the result you want: for an original variable A7LECTUR with values [1,2,1,4,-9], you'll get a miss_A7LECTUR column with values [0,0,0,0,1].

内容的提问来源于stack exchange，提问作者Gabriele Dente