Unordered Cartesian Product

Efficient version of expand.grid where order does not matter. This is a combinatorial variant where groups of elements are treated as equivalent regardless of order. For example, given: {1, 2}, {1, 2}, the unordered Cartesian product is {1, 1}, {1, 2}, {2, 2}. It is loosely equivalent to the following:

• t = expand.grid(lst)

• t = t[do.call(order, t), ]

• key = apply(t, 1, function(x) paste0(sort(x), collapse = ""))

• t[!duplicated(key), ]

comboGrid(..., repetition = TRUE, return_df = FALSE)

Arguments

...

vectors, factors or a list containing these. (See ?expand.grid).

repetition

Logical value indicating whether results should be with or without repetition. The default is TRUE.

return_df

Logical flag to force the output to be a data.frame. The default is FALSE.

Value

When all of the input is of the same type, by default comboGrid produce a matrix (a data.frame otherwise). This can be ignored by setting the argument return_df = TRUE.

Author

Joseph Wood

See also

expandGrid

Examples

## description example
lst = list(1:2, 1:2)

t = expand.grid(lst)
t = t[do.call(order, t), ]
key = apply(t, 1, function(x) paste0(sort(x), collapse = ""))
t[!duplicated(key), ]
#>   Var1 Var2
#> 1    1    1
#> 3    1    2
#> 4    2    2

## vs using comboGrid. N.B. Output is a matrix
comboGrid(lst)
#>      Var1 Var2
#> [1,]    1    1
#> [2,]    1    2
#> [3,]    2    2

## Force a data.frame to be returned
comboGrid(lst, return_df = TRUE)
#>   Var1 Var2
#> 1    1    1
#> 2    1    2
#> 3    2    2

## Input vectors are of different type, so a data.frame is returned
expGridNoOrder = comboGrid(1:5, 3:9, letters[1:5], letters[c(1,4,5,8)])
head(expGridNoOrder)
#>   Var1 Var2 Var3 Var4
#> 1    1    3    a    a
#> 2    1    3    a    d
#> 3    1    3    a    e
#> 4    1    3    a    h
#> 5    1    3    b    a
#> 6    1    3    b    d
tail(expGridNoOrder)
#>     Var1 Var2 Var3 Var4
#> 539    5    9    c    h
#> 540    5    9    d    d
#> 541    5    9    d    e
#> 542    5    9    d    h
#> 543    5    9    e    e
#> 544    5    9    e    h

expGridNoOrderNoRep = comboGrid(1:5, 3:9, letters[1:5],
                                letters[c(1,4,5,8)], repetition = FALSE)

head(expGridNoOrderNoRep)
#>   Var1 Var2 Var3 Var4
#> 1    1    3    a    d
#> 2    1    3    a    e
#> 3    1    3    a    h
#> 4    1    3    b    a
#> 5    1    3    b    d
#> 6    1    3    b    e
tail(expGridNoOrderNoRep)
#>     Var1 Var2 Var3 Var4
#> 401    5    9    c    d
#> 402    5    9    c    e
#> 403    5    9    c    h
#> 404    5    9    d    e
#> 405    5    9    d    h
#> 406    5    9    e    h