ggplot2 keep unused levels barplot

Question

I want to plot unused levels (that is, levels where the count is 0) in my bar-plot, however, unused levels are dropped and I cannot figure out how to keep them

df <- data.frame(type=c("A", "A", "A", "B", "B"), group=rep("group1", 5))
df$type <- factor(df$type, levels=c("A","B", "C"))

ggplot(df, aes(x=group, fill=type)) + geom_bar()

In the above example, I want to see C plotted with a count of 0, but it is completely absent...

Thanks for any help Ulrik

Edit:

This does what I want

df <- data.frame(type=c("A", "A", "A", "B", "B"), group=rep("group1", 5))
df1 <- data.frame(type=c("A", "A", "A", "B", "B", "A", "A", "C", "B", "B"), group=c(rep("group1", 5),rep("group2", 5)))

df$type <- factor(df$type, levels=c("A","B", "C"))
df1$type <- factor(df1$type, levels=c("A","B", "C"))
df <- data.frame(table(df))

df1 <- data.frame(table(df1))

ggplot(df, aes(x=group, y=Freq, fill=type)) + geom_bar(position="dodge")
ggplot(df1, aes(x=group, y=Freq, fill=type)) + geom_bar(position="dodge")

Guess the solution is to calculate the frequencies using table() and then plot

Answer 1

Does this do what you want?

ggplot(df, aes(x=type)) + geom_bar() + scale_x_discrete(drop=FALSE)