How to make a Sankey Diagram in R using this structure of data

Question

I have a particular structured data set on student performance across classes and into which achievement cohort they fell into. I want to create a sankey diagram that visualizes how students achievement cohorts changed across several classes. My data looks like this:

Course     St_ID    Achievement
Eng101     St_A     Top third
Eng101     St_B     Top third
Eng101     St_C     Middle third
Eng101     St_D     Middle third    
Eng101     St_E     Bottom third
Eng101     St_F     Bottom third
Calc101    St_A     Top third
Calc101    St_B     Bottom third
Calc101    St_C     Bottom third
Calc101    St_D     Top third
Calc101    St_E     Middle third
Calc101    St_F     Middle third
Hist101    St_A     Bottom third
Hist101    St_B     Bottom third
Hist101    St_C     Middle third
Hist101    St_D     Top third
Hist101    St_E     Middle third
Hist101    St_F     Top third

And I want the sankey diagram to look something like this (not drawn to scale):

How can I do that?

Answer 1

Here's a way to create this type of plot with ggalluvial

library(ggalluvial)

ggplot(df,
       aes(x = Course,
           label = Achievement,
           stratum = Achievement,
           alluvium = St_ID,
           fill = Achievement)) +
  geom_flow(stat = 'alluvium',
            lode.guidance = 'frontback') +
  geom_stratum()

^{Created on 2023-06-27 with reprex v2.0.2}