subsets of different vectors R

Question

I have three vectors as shown below.

q = c("a == 1", "a == 2", "a == 3")
w = c("b >= 50", "b >= 100")
t = c("c >= 40 & c <= 80", "c > 80")

I want to be able to combine all the vectors into one large vector so that every possible subset is in a larger vector. For example I want to have

("a == 1 & b >= 50", "a == 1 & b >= 100", "a ==2 & b >=50",
"a == 2 & b >= 100", "a == 3 & b >= 50", "a == 3 & b >= 100",
"a ==1 & c >= 40 & c <= 80", "a ==1 & c > 80",
"a ==2 & c >= 40 & c <= 80", "a ==2 & c > 80",
"a ==3 & c >= 40 & c <= 80", "a ==3 & c > 80",
"b  >= 50 & c >= 40 & c <= 80", "b >= 50 & c > 80",
"b  >= 100 & c >= 40 & c <= 80", "b >= 100 & c > 80", 
"a == 1 & b >= 50 & c >= 40 & c <= 80", "a == 1 & b >=50 & c > 80",
"a == 2 & b >= 50 & c >= 40 & c <= 80", "a == 2 & b >=50 & c > 80",
"a == 3 & b >= 50 & c >= 40 & c <= 80", "a == 3 & b >=50 & c > 80")
"a == 2 & b >= 100 & c >= 40 & c <= 80", "a == 2 & b >=100 & c > 80",
"a == 3 & b >= 100 & c >= 40 & c <= 80", "a == 3 & b >=100 & c > 80")

So I need every subset to be created and joined with the "&" sign but I don't want to be comparing any element in the same vector. I also have three vectors in this example but the number of vectors should be variable. Does anyone know how to achieve this? Thanks!

Answer 1

We can create strings using expand.grid and combn . Create a combn of list ('lst') elements picking 2 or 3 in a list (using lapply ), expand the list elements into a data.frame and paste with do.call (specifying the sep as " & " )

lst <- list(q w, t)
unlist( lapply(2:3, function(i) combn(lst, i, 
    FUN = function(x) do.call(paste, c(expand.grid(x), sep = " & ")), 
         simplify = FALSE)))