ggplot2 - bar plot with both stack and dodge

Here's an alternative take using faceting instead of dodging:

ggplot(df, aes(x = year, y = total, fill = type)) +
    geom_bar(position = "stack", stat = "identity") +
    facet_wrap( ~ treatment)

With Tyler's suggested change: + theme(panel.margin = grid::unit(-1.25, "lines"))

The closest you can get is by drawing a border around the dodged bars to highlight the stacked type values.

ggplot(df, aes(treatment, total, fill = year)) + 
geom_bar(stat="identity", position="dodge", color="black")

You can use interaction(year, treatment) as the x-axis variable as an alternative to dodge.

library(dplyr)
library(ggplot2)


df=data.frame(
  year=rep(c("2010","2011"),each=4),
  treatment=rep(c("Impact","Control")),
  type=rep(c("Phylum1","Phylum2"),each=2),
  total=sample(1:100,8)) %>% 
  mutate(x_label = factor(str_replace(interaction(year, treatment), '\\.', ' / '),
                          ordered=TRUE))

ggplot(df, aes(x=x_label, y=total, fill=type)) +
  geom_bar(stat='identity') +
  labs(x='Year / Treatment')

Created on 2018-04-26 by the reprex package (v0.2.0).

It can be done however its tricky/fiddly, you basically have to layer the bar chart.

here is my code:

library(tidyverse)

df=data.frame(
  year=rep(c(2010,2011),each=4),
  treatment=rep(c("Impact","Control")),
  type=rep(c("Phylum1","Phylum2"),each=2),
  total=sample(1:100,8))

# separate the by the variable which we are dodging by so 
# we have two data frames impact and control
impact <- df %>% filter(treatment == "Impact") %>% 
  mutate(pos = sum(total, na.rm=T))

control <- df %>% filter(treatment == "Control") %>% 
  mutate(pos = sum(total, na.rm=T))

# calculate the position for the annotation element
impact_an <- impact %>% group_by(year) %>% 
  summarise(
    pos = sum(total) + 12
    , treatment = first(treatment)
  )

control_an <- control %>% group_by(year) %>% 
  summarise(
    pos = sum(total) + 12
    , treatment = first(treatment)
  )

# define the width of the bars, we need this set so that
# we can use it to position the second layer geom_bar 
barwidth = 0.30

ggplot() +
  geom_bar(
    data = impact
    , aes(x = year, y = total, fill = type)
    , position = "stack"
    , stat = "identity"
    , width = barwidth
  ) + 
  annotate(
    "text"
    , x = impact_an$year
    ,y = impact_an$pos
    , angle = 90
    , label = impact_an$treatment
  ) +
  geom_bar(
    data = control
    # here we are offsetting the position of the second layer bar
    # by adding the barwidth plus 0.1 to push it to the right
    , aes(x = year + barwidth + 0.1, y = total, fill = type)
    , position = "stack"
    , stat = "identity"
    , width = barwidth
  ) +
  annotate(
    "text"
    , x = control_an$year + (barwidth * 1) + 0.1
    ,y = control_an$pos
    , angle = 90
    , label = control_an$treatment
  ) +
  scale_x_discrete(limits = c(2010, 2011))

This doesn't really scale well, however there are ways you could code it up to make it suit your situation, credit where its due I originally learnt this method from the following post: https://community.rstudio.com/t/ggplot-position-dodge-with-position-stack/16425