Extracting the Extended Model Frame from a Formula or Fit

This function attempts to apply model.frame and extend the result with columns of interactions.

Usage

extended.model.frame(formula, data, ..., sep = ".")

Arguments

formula

a model formula or terms object or an R object.

data

a data.frame, list or environment (see model.frame).

...

further arguments to pass to model.frame.

sep

separator in contraction of names for interactions (default = ".").

Value

A data.frame that includes everything a model.frame does plus interaction terms.

Examples

dat <- data.frame(Y = c(1,2,3,4,5,6), 
                  X = factor(LETTERS[c(1,1,2,2,3,3)]), 
                  W = factor(letters[c(1,2,1,2,1,2)]))
extended.model.frame(Y ~ X*W, dat)
#>   Y X W X:W
#> 1 1 A a A.a
#> 2 2 A b A.b
#> 3 3 B a B.a
#> 4 4 B b B.b
#> 5 5 C a C.a
#> 6 6 C b C.b