Order y-axis on ggforce::geom_parallel_sets

Question

Using the dev version of the ggforce package, I can create a Sankey diagram as follows (from the documentation)

data <- reshape2::melt(Titanic)
data <- gather_set_data(data, 1:4)

ggplot(data, aes(x, id = id, split = y, value = value)) +
  geom_parallel_sets(aes(fill = Sex), alpha = 0.3, axis.width = 0.1) +
  geom_parallel_sets_axes(axis.width = 0.1) +
  geom_parallel_sets_labels(colour = 'white')

What I'm struggling with, is getting the y-axis variables ordered in any way other than the default, which appears to be reverse alphabetical. For example, changing the plot so Adult appeared near the top of the plot, with Child below.

I've tried re-leveling the factors before applying gather_set_data, as well as re-leveling the y variable after applying gather_set_data, and neither appear to work. I've also tried defining them as characters and sorting in different orders but that also doesn't seem to work.

Any help would be appreciated.

Answer 1

Unsure what you would do with ggforce as I don't use this package. I assumed the solution would be to re-level the factors as you mentioned but this doesn't seem to be working for you. However, this does work with ggalluvial. Furthermore, there is an argument reverse that allows you to reverse the order (alphabetical/reverse alphabetical). See below:

Default ordering

library(ggplot2)
library(ggalluvial)

df <- as.data.frame(Titanic)

ggplot(as.data.frame(df),
       aes(weight = Freq,
           axis1 = Survived, axis2 = Sex, axis3 = Class)) +
  geom_alluvium(aes(fill = Class),
                width = 0, knot.pos = 1/4, reverse = FALSE) +
  guides(fill = FALSE) +
  geom_stratum(width = 1/8, reverse = FALSE) +
  geom_text(stat = "stratum", label.strata = TRUE, reverse = FALSE) +
  scale_x_continuous(breaks = 1:3, labels = c("Survived", "Sex", "Class")) +
  ggtitle("Titanic survival by class and sex")

Reverse ordering

ggplot(as.data.frame(df),
       aes(weight = Freq,
           axis1 = Survived, axis2 = Sex, axis3 = Class)) +
  geom_alluvium(aes(fill = Class),
                width = 0, knot.pos = 1/4, reverse = TRUE) +
  guides(fill = FALSE) +
  geom_stratum(width = 1/8, reverse = TRUE) +
  geom_text(stat = "stratum", label.strata = TRUE, reverse = TRUE) +
  scale_x_continuous(breaks = 1:3, labels = c("Survived", "Sex", "Class")) +
  ggtitle("Titanic survival by class and sex")

Re-leveling factor

df$Class <- factor(df$Class, levels = c("3rd", "1st", "Crew", "2nd"))

ggplot(as.data.frame(df),
       aes(weight = Freq,
           axis1 = Survived, axis2 = Sex, axis3 = Class)) +
  geom_alluvium(aes(fill = Class),
                width = 0, knot.pos = 1/4, reverse = FALSE) +
  guides(fill = FALSE) +
  geom_stratum(width = 1/8, reverse = FALSE) +
  geom_text(stat = "stratum", label.strata = TRUE, reverse = FALSE) +
  scale_x_continuous(breaks = 1:3, labels = c("Survived", "Sex", "Class")) +
  ggtitle("Titanic survival by class and sex")

Answer 2

How about changing y variable into factor as follows?

    titanic <- reshape2::melt(Titanic)
    titanic <- gather_set_data(titanic, 1:4)
    titanic$y <- factor(titanic$y, levels=c("Adult", "Child", "1st", "2nd", "3rd", "Crew", "Male", "Female", "Yes", "No"))
    ggplot(titanic, aes(x, id = id, split = y, value = value)) +
        geom_parallel_sets(aes(fill = Sex), alpha = 0.3, axis.width = 0.1) +
        geom_parallel_sets_axes(axis.width = 0.1) +
        geom_parallel_sets_labels(colour = 'white')