How to get all possible combination of column from the data frame?

Question

R> set.seed(123)
R> data <- matrix(rnorm(6),3,10)
R> colnames(data) <- c(\"s1\",\"s2\",\"s3\",\"s4\",\"s5\",\"s6\",\"s7\",\"s8\",\"s9\",\"s10\")
R>         


        

Answer 1

I have made a function to do this which comes in handy whenever I need it:

make_combinations <- function(x) {

  l <- length(x)
  mylist <- lapply(2:l, function(y) {
    combn(x, y, simplify = FALSE)
  })
  mylist

}


results <- make_combinations(colnames(data))
results[[1]]
# [[1]]
# [1] "s1" "s2"
# 
# [[2]]
# [1] "s1" "s3"
# 
# [[3]]
# [1] "s1" "s4"
# 
# [[4]]
# [1] "s1" "s5"
# 
# [[5]]
# [1] "s1" "s6"
# 
# [[6]]
# [1] "s1" "s7"
#and so on...

The function outputs a list, where each element is another list with all the 2-way, 3-way, 4-way... combinations. In your case it has 9 elements starting from the 2-way combinations all the way to the 10-way combination.