How to fix ordering of the sankey diagramm when using R ggalluvial, ggsankey package?

Question

Here is the input datasets:

id <- c("A1", "A2", "A3", "A4", "A5", "A6", "A7", "A8", "A9", "A10")
variation <- c("aaa1", "aaa1", "bbb1", "aaa2", "b1","a3", "a1", "b1", "a1", "b1" )
result <- c("Way1", "Way1", "Way2", "Way2", "Way3","Way1", "Way2", "Way3", "Way4", "Way1" )

data <- data.frame(id, variation, result)
head(data)

#     id variation result
# 1   A1      aaa1   Way1
# 2   A2      aaa1   Way1
# 3   A3      bbb1   Way2
# 4   A4      aaa2   Way2
# 5   A5        b1   Way3
# 6   A6        a3   Way1
# 7   A7        a1   Way2
# 8   A8        b1   Way3
# 9   A9        a1   Way4
# 10 A10        b1   Way1

Now lets prepare datasets for sankey diagramm while using R ggsankey package.

library(ggsankey)

data_df <- data %>%
  make_long(id, variation, result)
head(data_df)
# A tibble: 6 × 4
# x         node  next_x    next_node
# <fct>     <chr> <fct>     <chr>    
#   1 id        A1    variation aaa1     
# 2 variation aaa1  result    Way1     
# 3 result    Way1  NA        NA       
# 4 id        A2    variation aaa1     
# 5 variation aaa1  result    Way1     
# 6 result    Way1  NA        NA  

Now lets plot sankey diagramm using R ggalluvial package.

library(ggalluvial)


ggplot(data_df, aes(x = x, next_x = next_x, node = node, next_node = next_node, fill = factor(node), label = node)) +
  geom_alluvial(flow.alpha = .6) +
  geom_alluvial_text(size = 3, color = "black") +
  scale_fill_viridis_d() +
  theme_alluvial(base_size = 18) +
  labs(x = NULL) +
  theme(legend.position = "none",
        plot.title = element_text(hjust = .5)) +
  ggtitle("")

As we can see generated plot above, "id" variable ordering is not correct. A1, A10, A2 etc..

My question is how can I order "id" variable like A1, A2, A3 .. A10.

Thank you.

Answer 1

This is not special to ggsankey or ggalluvial. Your nodes are ordered alphabetically. To fix that you have to convert node to a factor with the order of the levels set in your desired order, e.g. to get the order as in your original data you could use forcats::fct_inorder:

data <- data.frame(id, variation, result)

library(ggsankey)
library(ggalluvial)
#> Loading required package: ggplot2
library(dplyr, warn=FALSE)
library(forcats)

data_df <- data %>%
  make_long(id, variation, result) |> 
  mutate(node = forcats::fct_inorder(node))

ggplot(data_df, aes(
  x = x, next_x = next_x, node = node,
  next_node = next_node, fill = node, label = node
)) +
  geom_alluvial(flow.alpha = .6) +
  geom_alluvial_text(size = 3, color = "black") +
  scale_fill_viridis_d() +
  theme_alluvial(base_size = 18) +
  labs(x = NULL) +
  theme(
    legend.position = "none",
    plot.title = element_text(hjust = .5)
  ) +
  ggtitle("")