Find elements not in smaller character vector list but in big list

Question

I have the two big and small list. I want to know which of the elements in big list are not in smaller list. The list consists of property

([1] \"character\"         


        

Answer 1

! only works on logical vectors. B is not logical, which is what causes the error. Decomposing the steps you're trying to make will show you this (i.e. !B). In this case, you want to use %in% (or match).

A[!A %in% B]

To decompose the above code:

1. A %in% B creates a logical vector that is TRUE for values of A that exist in B.
2. !A %in% B negates (reverses) the logic in (1)
3. A[!A %in% B] returns the vector of elements that are TRUE in (2)

Answer 2

Look at help("%in%") - there's an example all the way at the bottom of that page that addresses this situation.

A <- c("A", "B", "C", "D")
B <- c("A", "B", "C")
(new <- A[which(!A %in% B)])

# [1] "D"

EDIT:

As Tyler points out, I should take my own advice and read the support documents. which() is unnecessary when using %in% for this example. So,

(new <- A[!A %in% B])

# [1] "D"

Answer 3

While I think sets may help you to deal with different lists.

In your case, you can just use:

A <- c("A", "B", "C", "D")
B <- c("A", "B", "C")

# to find difference
setdiff(A, B)

# to find intersect
intersect(A, B)

# to find union
union(A, B)