How do I reorder the levels in this ggplot when the package I'm using forces the items into alphabetical order?

Question

Let me randomly generate some data with available packages to demonstrate my issue. I am using the randomForestSRC package to run some survival random forests, and I am plotting the results of the random forest as a ggplot using the ggRandomForests package. You'll see the plot I get at the very end.

I want my boxplots in the order "Yes", then "No", then "Maybe".

library(ggplot2)
library(ggRandomForests)
library(randomForestSRC)
library(survival)

df <- cancer # should grab the cancer data set from survival library

# Randomly generate some categorical data
var <- sample(c('Yes', 'No', 'Maybe'), 228, replace=TRUE)
df$var <- as.factor(var)

# Attempt to put them in the order I want (first yes, then no, then maybe)
df$var <- factor(df$var, levels = c("Yes", "No", "Maybe"))
levels(df$var) # Verify it is in order of "Yes", "No", "Maybe"

# Run survival random forests
rf <- rfsrc(Surv(time, status) ~ var, data = df,
            ntree = 1000, samptype = "swr", seed = 12345, membership = TRUE)

# Create a plot of the outcome, writing the plot object to a variable
pl <- plot.variable(rf, xvar.names = "var", partial = TRUE, 
                    surv.type = "years.lost", time = 365, show.plots = FALSE)

# Create a ggplot with the plot object with the ggRandomForests package
# Also tack on some labels to demonstrate how this code works
plot(gg_partial(pl)) + xlab("Category") + ylab("Outcome")

If you got what I got, then you should be seeing the plots in alphabetical order: Maybe, No, Yes. Which is, of course, NOT the order I wanted.

The only way I know to rearrange the order in a ggplot is to use that levels argument; I don't know of any other method for fixing this. Any ideas?

Answer 1

You could set the order via the limits argument of scale_x_discrete:

library(ggplot2)
library(ggRandomForests)
library(randomForestSRC)
library(survival)

plot(gg_partial(pl)) + 
  labs(x = "Category", y = "Outcome") +
  scale_x_discrete(limits = levels(df$var))