jtools (version 0.9.0)

probe_interaction: Probe interaction effects via simple slopes and plotting

Description

probe_interaction is a convenience function that allows users to call both sim_slopes and interact_plot with a single call.

Usage

probe_interaction(model, pred, modx, mod2 = NULL, ...)

Arguments

model

A regression model of type lm or svyglm. It should contain the interaction of interest.

pred

The predictor variable involved in the interaction.

modx

The moderator variable involved in the interaction.

mod2

Optional. The name of the second moderator variable involved in the interaction.

...

Other arguments accepted by sim_slopes and interact_plot

Value

simslopes

The sim_slopes object created.

interactplot

The ggplot object created by interact_plot.

Details

This function simply merges the nearly-equivalent arguments needed to call both sim_slopes and interact_plot without the need for re-typing their common arguments. Note that each function is called separately and they re-fit a separate model for each level of each moderator; therefore, the runtime may be considerably longer than the original model fit. For larger models, this is worth keeping in mind.

Sometimes, you may want different parameters when doing simple slopes analysis compared to when plotting interaction effects. For instance, it is often easier to interpret the regression output when variables are standardized; but plots are often easier to understand when the variables are in their original units of measure.

probe_interaction does not support providing different arguments to each function. If that is needed, use sim_slopes and interact_plot directly.

See Also

Other interaction tools: cat_plot, interact_plot, johnson_neyman, sim_slopes

Examples

# NOT RUN {
# Using a fitted model as formula input
fiti <- lm(Income ~ Frost + Murder * Illiteracy,
  data=as.data.frame(state.x77))
probe_interaction(model = fiti, pred = Murder, modx = Illiteracy,
                  modxvals = "plus-minus")
# 3-way interaction
fiti3 <- lm(Income ~ Frost * Murder * Illiteracy,
  data=as.data.frame(state.x77))
probe_interaction(model = fiti3, pred = Murder, modx = Illiteracy,
                  mod2 = Frost, mod2vals = "plus-minus")

# With svyglm
library(survey)
data(api)
dstrat <- svydesign(id = ~1, strata = ~stype, weights = ~pw,
                    data = apistrat, fpc = ~fpc)
regmodel <- svyglm(api00 ~ ell * meals + sch.wide, design = dstrat)
probe_interaction(model = regmodel, pred = ell, modx = meals,
                  modxvals = "plus-minus", cond.int = TRUE)

# 3-way with survey and factor input
regmodel3 <- svyglm(api00 ~ ell * meals * sch.wide, design = dstrat)
probe_interaction(model = regmodel3, pred = ell, modx = meals,
                  mod2 = sch.wide)
# Can try different configurations of 1st vs 2nd mod
probe_interaction(model = regmodel3, pred = ell, modx = sch.wide,
                  mod2 = meals)

# }