Strange ggplot behaviour - barplot columns are unordered and axis numbers are inconsistent

Question

I'm having some weird issues with ggplot in RStudio. This isn't the first time this has happened either.

I tried to create a reprex but wasn't able to reproduce the behaviour that I am getting in the figure below. (I've blanked out the y-axis labels for privacy)

Here's the code: pretty basic...

AED_screen_plot <- AED_num %>% 
  ggplot(aes(x = reorder(DHB,SCREENING.RATE), y = SCREENING.RATE, fill = AUDIT.YEAR)) +
  geom_bar(position = 'dodge', stat = 'identity') +
  ylab('Screening Rate (%)') +
  coord_flip()

print(AED_screen_plot)

And since I can't provide a simple reprex, here's the data...

data <- tibble('AUDIT.YEAR' = c(2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018), 'DHB' = c('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t'), 'SCREENING.RATE' = c(0,36,44,28,8,0,0,20,40,40,24,52,16,45,52,28,48,28,44,56,4,16,44,12,56,16,20,28,32,32,4,44,80,40,52,20,8,12,52,24))

What the hell am I doing wrong???? Why are the bar colours swapping around? Why is the x-axis munted? (Same thing happens without coord_flip().) Is it a data type problem or something? I've already tried converting everything to factors. Taking out the reorder() creates an identical graph.

Thanks very much. It's late Friday afternoon and I'm buggered.

Answer 1

I have used the following code and it works fine for me using the sample data provided by you. The only change I have made is that I have converted your year as a factor variable in place of default numeric or double.

library(tidyverse)

data <- tibble('AUDIT.YEAR' = c(2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2019,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018,2018), 'DHB' = c('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t'), 'SCREENING.RATE' = c(0,36,44,28,8,0,0,20,40,40,24,52,16,45,52,28,48,28,44,56,4,16,44,12,56,16,20,28,32,32,4,44,80,40,52,20,8,12,52,24))

data %>% 
  ggplot(aes(x = reorder(DHB,SCREENING.RATE), y = SCREENING.RATE, fill = factor(AUDIT.YEAR))) +
  geom_bar(position = 'dodge', stat = 'identity') +
  ylab('Screening Rate (%)') + xlab("DHB")+
  labs(fill='Year') + coord_flip()

If I you use year as such (numeric or continuous) variable it will give you the following plot

data %>% 
  ggplot(aes(x = reorder(DHB,SCREENING.RATE), y = SCREENING.RATE, fill = AUDIT.YEAR)) +
  geom_bar(position = 'dodge', stat = 'identity') +
  ylab('Screening Rate (%)') + xlab("DHB")+
  labs(fill='Year') + coord_flip()

Hope that helps you out.