fake_formula – gamlss2

Extended Processing of "Fake" Formulas

Description

Create a "fake" formula from a formula, a Formula, or a list of formulas. The function extracts all necessary variables (transformation of variables), to build a model.frame. The function also extracts all special model terms within the formulas, the information can be used to setup any special model term specification list.

Usage

fake_formula(formula, specials = NULL,
  nospecials = FALSE, onlyspecials = FALSE)

Arguments

`formula`	A `formula`, `Formula`, or a `list` of `formula`s.
`specials`	Character, vector of names of special functions in the formula, see `terms.formula`.
`nospecials`	Logical, should variables of special model terms be part of the "fake formula"?
`onlyspecials`	Logical, should only the special model terms be returned?

Value

Depending on the input formula, the function returns a formula or Formula. If onlyspecials = TRUE a vector or list of special model term names is returned.

Examples

library("gamlss2")

## basic formula
f <- y ~ x1 + x2 + log(x3)
ff <- fake_formula(f)
print(ff)

y ~ x1 + x2 + log(x3)

## including special model terms
f <- y ~ x1 + s(x2) + x3 + te(log(x3), x4)
ff <- fake_formula(f)
print(ff)

~x1 + x3 + x2 + log(x3) + x4

## multiple parts on the right-hand side
f <- y ~ x1 + s(x2) + x3 + te(log(x3), x4) | x2 + sqrt(x5)
ff <- fake_formula(f)
print(ff)

y ~ x1 + x3 + x2 + log(x3) + x4 | x2 + sqrt(x5)

## collapse all formula parts
print(formula(ff, collapse = TRUE))

y ~ x1 + x3 + x2 + log(x3) + x4 + (x2 + sqrt(x5))

print(formula(ff, collapse = TRUE, update = TRUE))

y ~ x1 + x3 + x2 + log(x3) + x4 + sqrt(x5)

## list of formulas
f <- list(
  y ~ x1 + s(x2) + x3 + te(log(x3), x4),
    ~ x2 + sqrt(x5),
    ~ z2 + x1 + exp(x3)
)
ff <- fake_formula(f)
print(ff)

y ~ x1 + x3 + x2 + log(x3) + x4 | x2 + sqrt(x5) | z2 + x1 + exp(x3)

## extract separate parts on the right-hand side
formula(ff, rhs = 1)

y ~ x1 + x3 + x2 + log(x3) + x4

formula(ff, rhs = 2)

y ~ x2 + sqrt(x5)

formula(ff, rhs = 3)

y ~ z2 + x1 + exp(x3)

## formula with multiple responses and multiple parts
f <- y1 | y2 | y3 ~ x1 + s(x2) + x3 + te(log(x3), x4) | x2 + ti(x5)
ff <- fake_formula(f)
print(ff)

y1 | y2 | y3 ~ x1 + x3 + x2 + log(x3) + x4 | x2 + x5

## list of formulas with multiple responses
f <- list(
  y1 ~ x1 + s(x2) + x3 + te(log(x3), x4),
  y2 ~ x2 + sqrt(x5),
  y3 ~ z2 + x1 + exp(x3) + s(x10)
)
ff <- fake_formula(f)

## extract only without special terms
ff <- fake_formula(f, nospecials = TRUE)
print(ff)

y1 | y2 | y3 ~ x1 + x3 | x2 + sqrt(x5) | z2 + x1 + exp(x3)

## extract only special terms
ff <- fake_formula(f, onlyspecials = TRUE)
print(ff)

[[1]]
[1] "s(x2)"          "te(log(x3),x4)"

[[2]]
character(0)

[[3]]
[1] "s(x10)"