rgsubleading-zero

Add leading zeros to colum names

I'm surprised to find no one asked this question on Stackoverflow before. Maybe it's too stupid to ask?

So I have a dataframe that contains 48 weather variables, each representing a weather value for a month. I have drawn a simplified table shown below:

weather 1 weather 2 weather 3 weather 4 weather 5 weather 6 weather 7 weather 8 weather 9 weather 10 weather 11 weather 12
12 6 34 9 100 .01 -4 38 64 77 21 34
99 42 -3 34 34 .5 27 19 7 18 NA 20

My objective is to make the column names from "weather 1, weather 2, ..." to "weather 01, weather 02, ...." And I wrote a loop like this:

for (i in 1:9){
  colnames(df) = gsub(i, 0+i, colnames(df))
}

However, instead of replacing the single-digit numbers with a leading zero, R replaced the actual letter "i" with "0+i". Can anyone let me know what's going on here and how to fix it? Or is there a better way to add leading zeros to column names?

Thank you very much!

Solution

  • We can use

    library(stringr)
colnames(df) <- str_replace(colnames(df), "\\d+", 
      function(x) sprintf("%02d", as.integer(x)))