Replace values in data.frame for multiple columns and merge

Question

Given the following data.frame df:

   Typ1 Typ2
    1    0         
    0    1         
    1    0  

And want to replace the values in each column where the value is set to 1 (is there a smarter possibility as the following?):

df["Typ1"][df["Typ1"] == 1]<-"Typ1"
df["Typ2"][df["Typ2"] == 1]<-"Typ2"

And merge the columns to:

   Typ 
  "Typ1"           
  "Typ2"           
  "Typ1"    

Answer 1

library(tidyr)
df %>% 
  pivot_longer(Typ1:Typ2, names_to = "Typ") %>% 
  filter(value == 1) %>% 
  select(Typ)

Output:

# A tibble: 3 × 1
  Typ  
  <chr>
1 Typ1 
2 Typ2 
3 Typ1 

Input:

df <- structure(list(Typ1 = c("1", "0", "1"), Typ2 = c("0", "1", "0"
)), row.names = 2:4, class = "data.frame")