R: Create a 'ffdf' from All Combinations of Factors

expand.ffgrid {ffbase} | R Documentation

## Create a `ffdf` from All Combinations of Factors

### Description

Similar as `expand.grid` in the base package generates an `ffdf`. Code is almost copy-pasted from `expand.grid`.

### Usage

    expand.ffgrid(..., KEEP.OUT.ATTRS = TRUE, stringsAsFactors = TRUE)

### Arguments

`...` | `ff` vectors, `ff` factors or a list containing these.
`KEEP.OUT.ATTRS` | currently ignored
`stringsAsFactors` | logical specifying if character vectors are converted to factors. Irrelevant for `ff` as character vectors are factors in package ff.

### Value

A `ffdf` containing one row for each combination of the supplied factors. The first factors vary fastest. The columns are labelled by the factors if these are supplied as named arguments or named components of a list.

### See Also

`expand.grid`

### Examples

    comb <- expand.ffgrid(ff(1:1000), ff(factor(LETTERS)))
    dim(comb)

    x <- ff(factor(LETTERS))
    y <- ff(1:1000)
    z <- ff(seq.Date(Sys.Date(), Sys.Date()+10, by = "day"))
    comb <- expand.ffgrid(x, y, z)
    dim(comb)
    comb[1:100, ]

    expand.ffgrid(list(a = ff(1:10), b = ff(1:10)))

[Package ffbase version 0.13.1 Index]