GGPLOT faceted bar plot: multiple "dodged" bars per fill-category?

Question

I'm plotting this data set 'ds'

ds <- structure(list(FN = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 
                            3L, 4L, 4L, 4L, 1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L, 4L, 4L, 4L, 
                            1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L, 4L, 4L, 4L, 1L, 1L, 1L, 2L, 
                            2L, 2L, 3L, 3L, 3L, 4L, 4L, 4L), .Label = c("FN=1", "FN=2", "FN=3", 
                            "FN=4"), class = "factor"), fraction = structure(c(1L, 1L, 1L, 
                            1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
                            1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
                            2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("serum", 
                            "plasma"), class = "factor"), demographics = structure(c(1L, 
                            1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 
                            2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
                            1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("not adjusted", 
                            "adjusted"), class = "factor"), freq = c(132, 47, 14, 30, 29, 
                    19, 25, 14, 9, 5, 4, 4, 24, 21, 15, 6, 6, 5, 4, 4, 2, 2, 2, 2, 
                    35, 28, 25, 68, 24, 11, 33, 15, 10, 12, 11, 8, 24, 16, 15, 13, 
                    10, 6, 7, 6, 5, 4, 3, 3)), .Names = c("FN", "fraction", "demographics", 
            "freq"), class = "data.frame", row.names = c(NA, -48L))

using this ggplot-code

ggplot(ds, aes(x=fraction, y=freq, fill=factor(demographics, c("adjusted", "not adjusted")))) + 
    geom_bar(position=position_dodge(width=0.9), stat="identity", color="black") + 
    facet_grid(FN~., switch="y") + 
    scale_fill_manual("", values=c("not adjusted"="#e41a1c", "adjusted"="#377eb8"), guide=guide_legend(reverse = TRUE)) + 
    theme_bw() + 
    theme(legend.title=element_blank(), legend.position="bottom") + 
    theme(axis.title.x=element_text(face="bold")) + 
    theme(axis.title.y=element_blank()) + 
    theme(axis.ticks=element_blank()) + 
    theme(panel.background=element_blank()) + 
    theme(panel.grid=element_blank()) + 
    theme(strip.text.y = element_text(angle=180)) + coord_flip() 

which returns this result

As you can see, there are three bars being stacked per x-variable 'fraction' (serum/plasma) and fill-category 'demographics' (not adjusted/adjusted). However, I would like these three bars per fill-category demographics to be plotted side by side. Is this even possible?

Your help is greatly appreciated!

Answer 1

Add a individual grouping variable

library("tidyverse")
ds %>% mutate(row = row_number()) %>% 
ggplot(aes(x=fraction, y=freq, fill=factor(demographics, c("adjusted", "not adjusted")), group = row)) + 
  geom_bar(position=position_dodge(width=0.9), stat="identity", color="black") + 
  facet_grid(FN~., switch="y") + 
  scale_fill_manual("", values=c("not adjusted"="#e41a1c", "adjusted"="#377eb8"), guide=guide_legend(reverse = TRUE)) + 
  theme_bw() + 
  theme(legend.title=element_blank(), legend.position="bottom") + 
  theme(axis.title.x=element_text(face="bold")) + 
  theme(axis.title.y=element_blank()) + 
  theme(axis.ticks=element_blank()) + 
  theme(panel.background=element_blank()) + 
  theme(panel.grid=element_blank()) + 
  theme(strip.text.y = element_text(angle=180)) + 
  coord_flip()