plot3logit (version 3.1.4)

plot3logit-package: Ternary Plots for Trinomial Regression Models

Description

An implementation of the ternary plot for interpreting regression coefficients of trinomial regression models, as proposed in santi2019;textualplot3logit. For details on the features of the package, see santi2022;textualplot3logit.

Compatibility

Function field3logit() can read trinomial regression estimates from the output of the following functions:

• clm and clm2 of package ordinal (ordinal logit regression);

• mlogit of package mlogit (logit regression);

• multinom of package nnet (logit regression);

• polr of package MASS (ordinal logit regression);

• vgam and vglm of package VGAM (logit regression).

Moreover, explicit estimates can be passed to field3logit(). See examples and functions field3logit() and extract3logit() for further details.

Author

Maintainer: Flavio Santi (ORCID)

Authors:

• Maria Michela Dickson (ORCID)

• Giuseppe Espa (ORCID)

• Diego Giuliani (ORCID)

Details

The package permits the covariate effects of trinomial regression models to be represented graphically by means of a ternary plot. The aim of the plots is helping the interpretation of regression coefficients in terms of the effects that a change in regressors' values has on the probability distribution of the dependent variable. Such changes may involve either a single regressor, or a group of them (composite changes), and the package permits both cases to be represented in a user-friendly way. Methodological details are illustrated and discussed in santi2019;textualplot3logit.

The package can read the results of both categorical and ordinal trinomial logit regression fitted by various functions (see extract3logit()) and creates a field3logit object which may be represented by means of functions autoplot() and plot().

The plot3logit package inherits graphical classes and methods from the package ggtern hamilton2018plot3logit which, in turn, is based on the ggplot2 package wickham2016aplot3logit.

Graphical representation based on standard graphics is made available through the package Ternary smith2017plot3logit by function TernaryField() and in particular by the method plot of field3logit class.

Since version 2.0.0, plot3logit can also compute and draw confidence regions associated to the covariate effects. See the vignette of the package (type vignette("plot3logit-overview")) and the help of function stat_conf3logit() for some examples.

References

See Also

field3logit(), gg3logit(), TernaryField().

Examples

# \donttest{
data(cross_1year)

# Read from "nnet::multinom" (categorical logit)
library(nnet)
mod0 <- multinom(employment_sit ~ gender + finalgrade, data = cross_1year)
field0 <- field3logit(mod0, 'genderFemale')
gg3logit(field0) + stat_field3logit()

# Read from "MASS::polr" (ordinal logit)
library(MASS)
mydata <- cross_1year
mydata$finalgrade <- factor(mydata$finalgrade,
  c('Low', 'Average', 'High'), ordered = TRUE)
mod1 <- polr(finalgrade ~ gender + irregularity, data = mydata)
field1 <- field3logit(mod1, 'genderFemale')
gg3logit(field1) + stat_field3logit()

# Read from list
mod2 <- list(
  B = matrix(
    data = c(-2.05, 0.46, -2.46, 0.37),
    nrow = 2,
    dimnames = list(c('(Intercept)', 'genderFemale'))
  ),
  levels = c('Employed', 'Unemployed', 'Trainee')
)
field2 <- field3logit(mod2, c(0, 1))
gg3logit(field2) + stat_field3logit()
# }