find_transformation: Find possible transformation of model variables

In easystats/insight: Easy Access to Model Information for Various Model Objects

Find possible transformation of model variables

Description

This functions checks whether any transformation, such as log- or exp-transforming, was applied to the response variable (dependent variable) in a regression formula. Optionally, all model terms can also be checked for any such transformation. Currently, following patterns are detected: log, log1p, log2, log10, exp, expm1, sqrt, ⁠log(y+<number>)⁠, log-log, power (e.g. to 2nd power, like I(y^2)), inverse (like 1/y), scale (e.g., y/3), and box-cox (e-g-, (y^lambda - 1) / lambda).

Usage

find_transformation(x, ...)

## Default S3 method:
find_transformation(x, include_all = FALSE, ...)

Arguments

x	A regression model or a character string of the formulation of the (response) variable.
...	Currently not used.
include_all	Logical, if TRUE, does not only check the response variable, but all model terms.

Value

A string, with the name of the function of the applied transformation. Returns "identity" for no transformation, and e.g. "log(y+3)" when a specific values was added to the response variables before log-transforming. For unknown transformations, returns NULL.

Examples

# identity, no transformation
model <- lm(Sepal.Length ~ Species, data = iris)
find_transformation(model)

# log-transformation
model <- lm(log(Sepal.Length) ~ Species, data = iris)
find_transformation(model)

# log+2
model <- lm(log(Sepal.Length + 2) ~ Species, data = iris)
find_transformation(model)

# find transformation for all model terms
model <- lm(mpg ~ log(wt) + I(gear^2) + exp(am), data = mtcars)
find_transformation(model, include_all = TRUE)

# inverse, response provided as character string
find_transformation("1 / y")

easystats/insight documentation built on Dec. 14, 2024, 12:34 p.m.