ggplot2 warning "removed x rows containing missing values" when drop = FALSE

Question

I am creating a side-by-side bar chart with ggplot2. My code produces the correct plot when scale_x_discrete(drop = T). However, I have a level with a value of 0, and I want to include this on the x-axis. When I set scale_x_discrete(drop = F), I get the warning: Removed x rows containing missing values (geom_bar). and another category with a non-zero value is shown as zero on the plot.

Here's a reprex of my data:

library("tidyverse")

df <- data.frame(
  location = c(rep("in", 231), rep("out", 83)),
  status = c(rep("normal", 73), rep("mild", 42), rep("moderate", 20), rep("fever", 4),
             rep("normal", 70), rep("mild", 41), rep("moderate", 62), rep("fever", 2)))

df$status <- factor(df$status, levels = c("normal", "mild", "moderate", "severe", "fever"))


df %>%
  ggplot(aes(x = status,
             y = ..count../tapply(..count.., ..x.., sum)[..x..],
             fill = location)) +
  geom_bar(position = "dodge") +
  scale_y_continuous(labels = scales::percent) +
  scale_x_discrete(drop=F) +
  NULL

I have been looking at this for ages and really cannot work out the problem.

Answer 1

Can't explain the non-zero values not plotting. Here is a solution using a dplyr's group_by functions

#calculate totals and then calculate the %
df %>% group_by(status, location) %>% summarise(value=n()) %>%   
  group_by(status) %>% mutate(result=value/sum(value)) %>%.      
  ggplot(aes(x = status,
             y = result,
             fill = location)) +
  geom_col(position = "dodge") +
  scale_y_continuous(labels = scales::percent) +
  scale_x_discrete(drop=F)

Notice this now geom_col and not geom_bar.