gratia: link – R documentation

Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!

link

Extract link and inverse link functions from models

Description

Returns the link or its inverse from an estimated model, and provides a simple way to extract these functions from complex models with multiple links, such as location scale models.

Usage

link(object, ...)

## S3 method for class 'family'
link(object, parameter = NULL, which_eta = NULL, ...)

## S3 method for class 'gam'
link(object, parameter = NULL, which_eta = NULL, ...)

## S3 method for class 'bam'
link(object, parameter = NULL, which_eta = NULL, ...)

## S3 method for class 'gamm'
link(object, ...)

## S3 method for class 'glm'
link(object, ...)

## S3 method for class 'list'
link(object, ...)

inv_link(object, ...)

## S3 method for class 'family'
inv_link(object, parameter = NULL, which_eta = NULL, ...)

## S3 method for class 'gam'
inv_link(object, parameter = NULL, which_eta = NULL, ...)

## S3 method for class 'bam'
inv_link(object, parameter = NULL, which_eta = NULL, ...)

## S3 method for class 'gamm'
inv_link(object, ...)

## S3 method for class 'list'
inv_link(object, ...)

## S3 method for class 'glm'
inv_link(object, ...)

extract_link(family, ...)

## S3 method for class 'family'
extract_link(family, inverse = FALSE, ...)

## S3 method for class 'general.family'
extract_link(family, parameter, inverse = FALSE, which_eta = NULL, ...)

Arguments

`object`	a family object or a fitted model from which to extract the family object. Models fitted by `stats::glm()`, `mgcv::gam()`, `mgcv::bam()`, `mgcv::gamm()`, and `gamm4::gamm4()` are currently supported.
`...`	arguments passed to other methods.
`parameter`	character; which parameter of the distribution. Usually `"location"` but `"scale"` and `"shape"` may be provided for location scale models. Other options include `"mu"` as a synonym for `"location"`, `"sigma"` for the scale parameter in `mgcv::gaulss()`, `"pi"` for the zero-inflation term in `mgcv::ziplss()`, `"power"` for the `mgcv::twlss()` power parameter, `"xi"`, the shape parameter for `mgcv::gevlss()`, `"epsilon"` or `"skewness"` for the skewness and `"delta"` or `"kurtosis"` for the kurtosis parameter for `mgcv::shash()`, or `"theta"` for the scale parameter of `mgcv::gammals()`.
`which_eta`	numeric; the linear predictor to extract for families `mgcv::mvn()` and `mgcv::multinom()`.
`family`	a family object, the result of a call to `family()`.
`inverse`	logical; return the inverse of the link function?

Author(s)

Gavin L. Simpson

Examples

load_mgcv()

link(gaussian())
link(nb())

inv_link(nb())


dat <- gamSim(1, n = 400, dist = "normal", scale = 2, verbose = FALSE)
mod <- gam(list(y ~ s(x0) + s(x1) + s(x2) + s(x3), ~ 1), data = dat,
           family = gaulss)

link(mod, parameter = "scale")
inv_link(mod, parameter = "scale")

## Works with `family` objects too
link(shash(), parameter = "skewness")

gratia

Graceful 'ggplot'-Based Graphics and Other Functions for GAMs Fitted Using 'mgcv'

v0.6.0

MIT + file LICENSE

Authors

Gavin L. Simpson [aut, cre] (<https://orcid.org/0000-0002-9084-8413>), Henrik Singmann [ctb] (<https://orcid.org/0000-0002-4842-3657>)

Initial release

2021-04-17