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Change character values under specific columns that ends with similar suffixes in R

December 15, 2022

Hello friends I have a data frame like this:

# Define the column names
col_names <- c("A_1C_1", "B_1C_1", "C_1C_1", "D_1C_1", "E_1C_1", "F_1C_1", "G_1C_1", "H_1E_1", "I_1D_1", "J_1D_1")

# Define the data frame
df <- data.frame(replicate(10, sample(c("apple", "banana", "kiwi", "milk"), 10, replace = TRUE)),
                 stringsAsFactors = FALSE)
# Set the column names
colnames(df) <- col_names
df
    A_1C_1 B_1C_1 C_1C_1 D_1C_1 E_1C_1 F_1C_1 G_1C_1 H_1E_1 I_1D_1 J_1D_1
1    milk   kiwi   kiwi banana banana   kiwi banana   kiwi banana   kiwi
2    milk banana banana   milk banana banana   milk banana  apple   kiwi
3    milk banana banana   kiwi banana banana banana banana banana banana
4    milk   kiwi  apple banana   kiwi banana   kiwi   kiwi banana   milk
5    milk  apple   kiwi banana banana banana banana banana   milk   milk
6    kiwi banana banana  apple   kiwi banana   kiwi   kiwi banana   milk
7    kiwi  apple  apple   milk   milk banana   milk   milk   kiwi banana
8  banana   kiwi   kiwi   milk  apple  apple   milk  apple  apple   milk
9    milk  apple   kiwi   milk   milk banana   milk   kiwi   kiwi   milk
10   milk   kiwi  apple   milk banana   kiwi banana   kiwi   milk banana

What I want to do is to change character values under the columns that end with C_1 in a way that apple will be sweet-sour,
banana will be sweet,
kiwi will be sour and
milk will turn to tasteless.

how can I do that?
Thanks a lot!

>Solution :

You can use across inside mutate to apply a function (.fns) across multiple variables, given the condition you want (.cols).

library(dplyr)

df %>% 
  mutate(
    across(
      .cols = ends_with("C_1"),
      .fns = ~case_when(
        . == "apple" ~ "sweet sour",
        . == "banana" ~ "sweet",
        . == "kiwi" ~ "sour",
        . == "milk" ~ "tasteless"
      )
    )
  )