How to create new dataframe column with a character that comes from three other columns but only if present in a list, in R

Question

I've been trying to do this with mutate(), str_detect(), but it's too complex and dont know how to do all the steps, please help!

I have a dataframe in which 3 cols contain let's say fruits, animals, or "none".

col1	col2	col3
apple	cat	none
apple	dog	none
pear	none	none
pear	apple	none
none	none	none

And then I have two lists:

fruit <- c("apple", "pear", banana") animal <- c("cat", "dog", "sheep")

I want to create two new columns in the dataframe: col4 should display only fruits from col1, col2, col3. If more than one fruit, I need them separated by commas. col5 does the same but for animals. If col1, col2, col3 dont contain an animal or a fruit, I need col4 and col5 to say "none".

col1	col2	col3	col4	col5
apple	cat	none	apple	cat
cat	dog	none	none	cat, dog
pear	none	none	pear	none
pear	apple	none	pear, apple	none
none	none	none	none	none

Answer 1

This gives you what you want:

df <- data.frame(col1=c("apple", "cat", "pear", "pear","none"),
                 col2=c("cat", "dog", "none", "apple", "none"),
                 col3 = c("none", "none", "none", "none", "none"))

fruit <- c("apple", "pear", "banana")
animal <- c("cat", "dog", "sheep")

df %>% mutate(col4 = apply(.,1, function(x) paste0(x[x != "none" & x %in% fruit], collapse = ",")),
              col5 = apply(.,1, function(x) paste0(x[x != "none" & x %in% animal], collapse = ",")),
              across(.cols = c("col4", "col5"), .fns = ~replace(.x, .x == "", "none")))

output:

  col1  col2 col3       col4    col5
1 apple   cat none      apple     cat
2   cat   dog none       none cat,dog
3  pear  none none       pear    none
4  pear apple none pear,apple    none
5  none  none none       none    none

``