Joining 2 bar columns in barcharts with curved line-CodePudding

I have below ggplot:

library(ggplot2)
data = rbind(data.frame('val' = c(10, 30, 15), 'name' = c('A', 'B', 'C'), group = 'gr1'), data.frame('val' = c(30, 40, 12), 'name' = c('A', 'B', 'C'), group = 'gr2'))
ggplot(data,                         # Draw barplot with grouping & stacking
       aes(x = group,
           y = val,
           fill = name))   
  geom_bar(stat = "identity",
           position = "stack", width = .1)

With this, I am getting below plot

However, I want to connect these bars with a curved area where the area would be equal to the value of the corresponding bar-component. A close example could be like,

Is there any way to achieve this with ggplot?

Any pointer will be very helpful.

CodePudding user response：

This is something like an alluvial plot. There are various extension packages that could help you create such a plot, but it is possible to do it in ggplot directly using a bit of data manipulation.

library(tidyverse)

alluvia <- data %>%
  group_by(name) %>%
  summarize(x = seq(1, 2, 0.01),
            val = pnorm(x, 1.5, 0.15) * diff(val)   first(val))

ggplot(data,                        
       aes(x = as.numeric(factor(group)),
           y = val,
           fill = name))  
    geom_bar(stat = "identity",
             position = "stack", width = .1)  
  geom_area(data = alluvia, aes(x = x), position = "stack", alpha = 0.5)  
  scale_x_continuous(breaks = 1:2, labels = levels(factor(data$group)),
                     name = "Group", expand = c(0.25, 0.25))  
  scale_fill_brewer(palette = "Set2")  
  theme_light(base_size = 20)