Examples of generating combinations

Randy Lai

2020年01月08日

1. combinations: without replacement: distinct items

I <-iterpc(5, 2)
getall(I)

## [,1] [,2]
## [1,] 1 2
## [2,] 1 3
## [3,] 1 4
## [4,] 1 5
## [5,] 2 3
## [6,] 2 4
## [7,] 2 5
## [8,] 3 4
## [9,] 3 5
## [10,] 4 5

2. combinations: with replacement: distinct items

I <-iterpc(5, 2, replace = TRUE)
getall(I)

## [,1] [,2]
## [1,] 1 1
## [2,] 1 2
## [3,] 1 3
## [4,] 1 4
## [5,] 1 5
## [6,] 2 2
## [7,] 2 3
## [8,] 2 4
## [9,] 2 5
## [10,] 3 3
## [11,] 3 4
## [12,] 3 5
## [13,] 4 4
## [14,] 4 5
## [15,] 5 5

3. combinations: without replacement: non distinct items

x <-c("a", "a", "b", "c")
I <-iterpc(table(x), 2)
# or I <- iterpc(c(2,1,1), 2, label=c("a", "b", "c"))
getall(I)

## [,1] [,2]
## [1,] 1 1
## [2,] 1 2
## [3,] 1 3
## [4,] 2 3

4. combinations: with replacement: non distinct items

x <-c("a", "a", "b", "c")
I <-iterpc(table(x), 2, replace = TRUE)
# or I = iterpc(c(2,1,1), 2, label=c("a", "b", "c"), replace=TRUE)
getall(I)

## [,1] [,2]
## [1,] 1 1
## [2,] 1 2
## [3,] 1 3
## [4,] 2 2
## [5,] 2 3
## [6,] 3 3