how to add percent column to every other column in dataframe in R

April 21, 2022

I have adataframe of counts and I want to add % column after each count column.

df <- data.frame(name= c("Ji", "Ka", "Na", "Po"),
                 `a(N)`= c(1,4,5,2),
                 `b(N)`=c(0.5,04,0.8,0.3),
                 `c(N)`= c(41,49,48,42))

df
  name a.N. b.N. c.N.
1   Ji    1  0.5   41
2   Ka    4  4.0   49
3   Na    5  0.8   48
4   Po    2  0.3   42

so I want something like

df <- df %>%
  add_column(`a(%)` = df$a.N./sum(df$a.N.), .after= "a.N.") %>%
  add_column(`b(%)` = df$b.N./sum(df$b.N.), .after= "b.N.") %>%
  add_column(`c(%)` = df$c.N./sum(df$c.N.), .after= "c.N.")

  name a.N.       a(%) b.N.       b(%) c.N.      c(%)
1   Ji    1 0.08333333  0.5 0.08928571   41 0.2277778
2   Ka    4 0.33333333  4.0 0.71428571   49 0.2722222
3   Na    5 0.41666667  0.8 0.14285714   48 0.2666667
4   Po    2 0.16666667  0.3 0.05357143   42 0.2333333

My actual dataframe has many more columns so it does not make sense to apply add_column one by one. is there a way to get the percent columns with fewer lines of codes?

>Solution :

We may use across

library(dplyr)
library(stringr)
df %>% 
   mutate(across(-name, ~ .x/sum(.x),
    .names = "{str_remove(.col, fixed('.N.'))}(%)"))  %>%
   select(name, gtools::mixedsort(names(.)[-1]))

-output

   name a.N.       a(%) b.N.       b(%) c.N.      c(%)
1   Ji    1 0.08333333  0.5 0.08928571   41 0.2277778
2   Ka    4 0.33333333  4.0 0.71428571   49 0.2722222
3   Na    5 0.41666667  0.8 0.14285714   48 0.2666667
4   Po    2 0.16666667  0.3 0.05357143   42 0.2333333