Compare two character vectors in R

Question

I have two character vectors of IDs.

I would like to compare the two character vectors, in particular I am interested in the following figures:

• How many IDs are both in A and B
• How many IDs are in A but not in B
• How many IDs are in B but not in A

I would also love to draw a Venn diagram.

Answer 1

Here are some basics to try out:

> A = c("Dog", "Cat", "Mouse") > B = c("Tiger","Lion","Cat") > A %in% B [1] FALSE  TRUE FALSE > intersect(A,B) [1] "Cat" > setdiff(A,B) [1] "Dog"   "Mouse" > setdiff(B,A) [1] "Tiger" "Lion"  

Similarly, you could get counts simply as:

> length(intersect(A,B)) [1] 1 > length(setdiff(A,B)) [1] 2 > length(setdiff(B,A)) [1] 2 

Answer 2

I'm usually dealing with large-ish sets, so I use a table instead of a Venn diagram:

xtab_set <- function(A,B){     both    <-  union(A,B)     inA     <-  both %in% A     inB     <-  both %in% B     return(table(inA,inB)) }  set.seed(1) A <- sample(letters[1:20],10,replace=TRUE) B <- sample(letters[1:20],10,replace=TRUE) xtab_set(A,B)  #        inB # inA     FALSE TRUE #   FALSE     0    5 #   TRUE      6    3