Hey there! Let's break down why your original renaming loop failed and walk through a couple of solid solutions.

Why Your Original Code Didn't Work #

The issue with your second loop is that names(data.frame(...))[1:3] <- names is an assignment operation that returns the vector of column names you just set, not the modified data frame. So when you wrap that in assign(), you're actually overwriting mydf1/mydf2/mydf3 with a string vector instead of the updated data frame.

Solution 1: Fix the Loop to Modify Existing Data Frames #

Instead of trying to do everything in one line, split the process into three clear steps: grab the existing data frame, update its column names, then save it back to the global environment. Here's how:

# First, run your original code to create empty data frames
for(i in 1:3){ 
  assign(paste0("mydf",i), data.frame(matrix("", nrow = 3, ncol = 3))) 
}

# Now fix the column names with this loop
for(i in 1:3){
  # Get the existing data frame from the global environment
  current_df <- get(paste0("mydf", i))
  # Update the column names
  names(current_df) <- c("n1", "n2", "n3")
  # Save the modified data frame back
  assign(paste0("mydf", i), current_df)
}

Solution 2: Use a List (Recommended!) #

Creating multiple separate data frames in the global environment can get messy fast. A better practice is to store them in a list—this makes future operations (like modifying, analyzing, or exporting) way easier. Here's how to do it in one go:

# Create a list of empty data frames with the correct column names
mydf_list <- lapply(1:3, function(x) {
  # Create empty data frame
  df <- data.frame(matrix("", nrow = 3, ncol = 3))
  # Set column names immediately
  names(df) <- c("n1", "n2", "n3")
  return(df)
})

# If you really need them as separate objects in the global environment (not ideal, but possible)
names(mydf_list) <- paste0("mydf", 1:3)
list2env(mydf_list, envir = .GlobalEnv)

Using a list keeps your workspace clean, and you can loop through the list elements directly without relying on get() and assign()—which are generally best avoided for routine tasks.

内容的提问来源于stack exchange，提问作者youraz