argument "second_str" is missing with no default - r

Question

I have written a function which finds the intersection between two strings. I want to use this function in apply and find out all the intersections in the given data frame. I am using below code.
Function:-
common <- function(first_str,second_str)
{
a <- unlist(strsplit(first_str," "))
b <- unlist(strsplit(second_str," "))
com <- intersect(a,b)
return((length(com)/length(union(a,b)))*100)
}
Data frame:-
str1 <- c("One Two Three","X Y Z")
str2 <- c("One Two Four", "X Y A")
df <- data.frame(str1, str2)
When use apply I get argument "second_str" is missing with no default error
apply(df, 1, common)
Could you please help me out with the solution?

Answer 1

apply() will only pass a single vector to the function you provide. With margin=1 it will call your function once per each row with a single vector containing all the values for the "current" row. It will not split up those values into multiple parameters to your function.
You could instead re-write your function to
common2 <- function(x) {
first_str <- x[1]
second_str <- x[2]
a <- unlist(strsplit(first_str," "))
b <- unlist(strsplit(second_str," "))
com <- intersect(a,b)
return((length(com)/length(union(a,b)))*100)
}
Although that doesn't scale well for multiple parameters. YOu could also use Map or mapply to iterate over multiple vectors at a time
If your original function you can do
with(df, Map(common, str1, str2))