Loop over multiple character columns to derive a new variable

Could you please help me with a code in R. I want to derive a new variable available with values as Yes or No, however it need to check the character variables a1, a2, a3, a4 and whichever variable has a value as ‘yellow’ then available variable should be yes else no.

a1 <- c('orange','red') 
a2 <- c('red','yellow') 
a3 <- c('black','orange') 
a4 <- c('red','brown')

testa <- data.frame(a1,a2,a3,a4)

>Solution :

dplyr

You may use rowwise and c_across:

testa %>% 
  rowwise() %>% 
  mutate(available = ifelse(any(c_across(a1:a4) == "yellow"), "yes", "no"))

  a1     a2     a3     a4    available
  <chr>  <chr>  <chr>  <chr> <chr>    
1 orange red    black  red   no       
2 red    yellow orange brown yes      

base R

Use apply:

testa$available <- apply(testa, 1, function(x) ifelse(any(x == "yellow"), "yes", "no"))