Adjusting Johnson-Neyman Plots

I used the interactions package to run a Johnson-Neyman analysis to probe an interaction.

I received an output including a plot of the analysis.

I struggle to change some of the parameters (I think this is not a usual ggplot syntax).

Specifically, I want to:

Change the scaling on the x and y axis (so y = -1, 0, 1 and x = 1, 2, 3, 4, 5, 6, 7)

Change the color scheme to grayscale.

Center the plot title.

This is my code so far:

library(interactions)

data <- read.csv("C:/Users/Itai/Desktop/1.csv")

test <- lm(choose_town ~ cond_num * CFNU, data = data)

summary(test)

y <- johnson_neyman(model = test, pred = cond_num, modx = CFNU)

y <- y[["plot"]]

y[["labels"]][["x"]] <- "CNFU"

y[["labels"]][["y"]] <- "Donation Destination"

y[["coordinates"]][["limits"]][["x"]] <- c(1, 7)

y[["coordinates"]][["limits"]][["y"]] <- c(-1, 1)

y[["labels"]][["title"]] <- "Johnson-Neyman Plot"

y

I do not have your data, so I use one of their examples instead. Their documentation is a bit confusing and yes they return a ggplot object, but y itself cannot be chained as you are used to in ggplot2

You already noticed that the ggplot part resides in y[["plot"]] so when done and you just want to format your graph you can use ggplot chaining from there.

library(interactions)

states <- as.data.frame(state.x77)

fiti <- lm(Income ~ Illiteracy * Murder + `HS Grad`, data = states)

y <- johnson_neyman(fiti, pred = Illiteracy, modx = Murder, alpha = .05, plot = F)

y[["plot"]] +
  labs(title = "My new Johnson-Neyman Plot title", x = "My new x axis", y = "My new y axis") +
  xlim(-10, 16) +
  ylim(-1500, 1500)