Loop through columns and add string lengths as new columns

Question

I have a data frame with a number of columns  and would like to output a separate column for each with the length of each row in it   I am trying to iterate through the column names  and for each column output a corresponding column with   length  attached   For example col1   col2 would go to col1   col2   col1 length   col2 length  The code I am using is   df  lt - data frame col1   c  abc   abcd   a   abcdefg   col2   c  adf qqwe   d   e   f     for i in names df      df paste i  length  sep       lt - str length df i       However this throws and error       invalid function in complex assignment    Am I able to use loops in this way in R

User · Answer

For the sake of completeness  there is also a data table solution   library data table  result  lt - setDT df    paste0 names df     length      lapply  SD  stringr  str length   result        col1     col2 col1 length col2 length  1      abc adf qqwe           3           8  2     abcd        d           4           1  3        a        e           1           1  4  abcdefg        f           7           1

User · Answer

You can use lapply to pass each column to str length  then cbind it to your original data frame     library stringr   out  lt - lapply  df   str length       df  lt - cbind  df   out          col1     col2 col1 col2  1     abc adf qqwe    3    8  2    abcd        d    4    1  3       a        e    1    1  4 abcdefg        f    7    1

User · Answer

You need to use      the programmatic equivalent of    Otherwise  for example  when i is col1  R will look for df i instead of df col1   for i in names df      df  paste i   length   sep         lt - str length df  i

User · Answer

With dplyr and stringr you can use mutate all    gt  df   gt   mutate all funs length   str length            col1     col2 col1 length col2 length 1     abc adf qqwe           3           8 2    abcd        d           4           1 3       a        e           1           1 4 abcdefg        f           7           1

[r] Loop through columns and add string lengths as new columns

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