Stacked bar chart: How to arrange the groups with forcats package

Question

I am working a making som nice plots that I can copy-paste when needed (that is why I have included so many options). So I have this plot:

library(tidyverse)
    mtcars %>% 
      group_by(cyl) %>% 
      summarise(n=n()) %>% 
      ungroup() %>% 
      mutate(cars = "cars") %>% 
      ggplot(aes(x = as.factor(cars), y = n, fill=as.factor(cyl))) +
      geom_bar(stat="identity", width = .3) +
      geom_text(aes(label = paste0(round(n, digits = 0), "stk.")),
                position = position_stack(vjust = 0.5)) +
      labs(title = "Number of cars with cylinders in the data set", 
           subtitle= "If needed",
           caption= "Fodnote",
           x= "", y="Antal",
           fill="# of cylinders") +
      theme(#legend.position="none",
            plot.caption = element_text(hjust = 0))

How can I reorder the stacks so e.g. the blue is at the bottom, then the red stack and the green stack on top. Thanks. I think the solution involes forcats...

Answer 1

Is this what you're looking for? To change the fill color, use scale_fill_manual() or scale_fill_brewer()

library(tidyverse)
library(forcats)

mtcars %>% 
  group_by(cyl) %>% 
  summarise(n=n()) %>% 
  ungroup() %>% 
  mutate(cars = "cars",
         cars = factor(cars),
         cyl  = factor(cyl)) %>% 

  # use fct_reorder here
  mutate(cyl = fct_reorder(cyl, n)) %>% 

  ggplot(aes(x = cars, y = n, fill = cyl)) +
  geom_col(width = .3) +
  geom_text(aes(label = paste0(round(n, digits = 0), "stk.")),
            position = position_stack(vjust = 0.5)) +
  labs(title = "Number of cars with cylinders in the data set", 
       subtitle = "If needed",
       caption = "Footnote",
       x = "", y = "Antal",
       fill = "# of cylinders") +
  theme(#legend.position="none",
    plot.caption = element_text(hjust = 0))