Adding section titles between tick labels in a horizontal bar plot

Question

I am trying to make a horizontal grouped bar plot showing how people have answered different questions.

Is there a way I can divide the questions into sections, putting a bold heading above each section stating what it is? Preferably without it resulting in separate plot areas the way it would if I used panels.

For the example below, suppose the headings I want to insert are "Vowels" and "Consonants" (hand-drawn in red in the picture in this example)

library('ggplot2')
library('stringr')
set.seed(5)

questions <- str_wrap(c('Blah blah blah blah blah blah B?',
                        'Blbbity blah blibbity blah C?',
                        'Blah blah blibbity blah blah blah D?',
                        'Blah blah blah A?',
                        'Blah blah blah blibbity E?',
                        'Blah blah blibbity blah I?'),15)

status <- data.frame(matrix(data=NA, nrow=18,ncol=3))
names(status) <- c('varname','type','percent')
status['varname'] <- factor(c(rep(1,3),rep(2,3),rep(3,3),rep(4,3),rep(5,3),rep(6,3)),labels=questions)
status['type'] <- c(rep(c('Cohabiting','Married','Divorced'),6))
status['percent'] <- c(rnorm(18,.5,.2))
ggplot(status, aes(varname, percent)) +   
  theme(axis.title.y = element_blank(), legend.title = element_blank(), plot.title = element_text(hjust = 0.5), legend.position = "top") +
  geom_bar(aes(fill = type), position = "dodge", stat="identity") + coord_flip() + scale_fill_manual(values=c('cadetblue1','cadetblue3','darkcyan')) +
  ggtitle('By couple type') + labs(y='Percent') + ylim(0,1)

Answer 1

You can tweak facet_grid() plot to remove all the panels to your liking.

If you want a y-axis across facets, see this answer

library(dplyr)
library("ggplot2")
library("stringr")

# create new alp variable
status <- status %>% 
  # edit: shamelessly steal from Maurits's answer :-)
  mutate(alp = if_else(str_detect(varname, "(I|E|A)\\?$"), "Vowels", "Consontants"))

p2 <- ggplot(status, aes(varname, percent)) +
  geom_col(aes(fill = type), position = "dodge") + 
  facet_grid(alp ~ ., scales = 'free_y', space = 'free_y', switch = 'y') +
  coord_flip() + 
  scale_fill_manual(values = c("cadetblue1", "cadetblue3", "darkcyan"),
                    # increase the spacing between legend key text
                    labels = stringr::str_pad(status$type, 5, "right"),) +
  ggtitle("By couple type") + 
  labs(y = "Percent") + 
  scale_x_discrete(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0), limits = c(0, 1)) +
  theme_classic(base_size = 14, base_family = 'mono') +
  theme(axis.title.y = element_blank(), 
        legend.spacing.x = unit(0.25, unit = "cm"),
        legend.title = element_blank(), 
        plot.title = element_text(hjust = 0.5), 
        legend.position = "top") +
  theme(panel.grid.minor.x = element_blank()) + 
  # switch the facet strip label to outside 
  theme(strip.placement = 'outside',
        strip.text.y = element_text(face = 'bold'),
        strip.background.y = element_rect(colour = NA, fill = 'grey80'))
p2

p3 <- ggplot(status, aes(varname, percent)) +
  geom_col(aes(fill = type), position = "dodge") + 
  facet_grid(alp ~ ., scales = 'free_y', space = 'free_y', switch = 'y') +
  coord_flip() + 
  scale_fill_manual(values = c("cadetblue1", "cadetblue3", "darkcyan"),
                    # increase the spacing between legend key text
                    labels = stringr::str_pad(status$type, 5, "right"),) +
  ggtitle("By couple type") + 
  labs(y = "Percent") + 
  scale_x_discrete(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0), limits = c(0, 1)) +
  theme_classic(base_size = 14, base_family = 'mono') +
  theme(axis.title.y = element_blank(), 
        legend.spacing.x = unit(0.25, unit = "cm"),
        legend.title = element_blank(), 
        plot.title = element_text(hjust = 0.5), 
        legend.position = "top") +
  theme(panel.grid.minor.x = element_blank()) + 
  # switch the facet strip label to outside 
  # remove background color
  theme(strip.placement = 'outside',
        strip.text.y = element_text(face = 'bold'),
        strip.background.y = element_blank())
p3

^{Created on 2018-10-02 by the reprex package (v0.2.1.9000)}

Answer 2

How about using facets?

library(tidyverse)
status %>%
    mutate_if(is.factor, as.character) %>%
    mutate(Group = if_else(str_detect(varname, "(I|E|A)\\?$"), "Vowels", "Consontants")) %>%
    ggplot(aes(varname, percent)) +
    theme(
        axis.title.y = element_blank(),
        legend.title = element_blank(),
        plot.title = element_text(hjust = 0.5),
        legend.position = "top") +
  geom_bar(aes(fill = type), position = "dodge", stat = "identity") +
  facet_wrap(~Group, ncol = 1, scales = "free_y") +
  coord_flip() +
  scale_fill_manual(values = c('cadetblue1', 'cadetblue3', 'darkcyan')) +
  ggtitle('By couple type') +
  labs(y = 'Percent') +
  ylim(0, 1)

Or you can move the strip labels to the left:

library(tidyverse)
status %>%
    mutate_if(is.factor, as.character) %>%
    mutate(Group = if_else(str_detect(varname, "(I|E|A)\\?$"), "Vowels", "Consontants")) %>%
    ggplot(aes(varname, percent)) +
    theme(
        axis.title.y = element_blank(),
        legend.title = element_blank(),
        plot.title = element_text(hjust = 0.5),
        legend.position = "top") +
  geom_bar(aes(fill = type), position = "dodge", stat = "identity") +
  facet_wrap(~Group, ncol = 1, scales = "free_y", strip.position = "left") +
  coord_flip() +
  scale_fill_manual(values = c('cadetblue1', 'cadetblue3', 'darkcyan')) +
  ggtitle('By couple type') +
  labs(y = 'Percent') +
  ylim(0, 1)