ggplot2 using the coord_polar()_error observed

Question

I'm trying draw a pie chart with ggplot2, using coord_polar. However I'm getting an error message as below.

Error in unique.default(x, nmax = nmax) : unique() applies only to vectors

Below is the code which I was using.Can someone please advise what's causing this error

freqtable <- table(worms$Vegetation)
df <- as.data.frame.table(freqtable)
colnames(df)<-c("Vegetation","Frequency")
pie<- ggplot(df, aes(x = "", fill = factor(class))) +
geom_bar(width = 1) +  theme(axis.line = element_blank(),plot.title = element_text(hjust=0.5)) +
labs(fill="class",x=NULL, y=NULL, title="Pie Chart of Vegetation", caption="Source: Worms")
pie+coord_polar(theta = "y", start=0)

Thanks and regards, Rahim

Answer 1

Say your data frame is like this:

worms = data.frame(Vegetation=sample(letters[1:4],100,replace=TRUE))

as.data.frame.table(table(worms$Vegetation))
  Var1 Freq
1    a   22
2    b   30
3    c   21
4    d   27

You don't need to tabulate, just provide the category as argument to fill = :

ggplot(worms, aes(x = "", fill = Vegetation)) +
geom_bar(width = 1) +  
theme(axis.line = element_blank(),plot.title = element_text(hjust=0.5)) + 
coord_polar(theta = "y", start=0) +
labs(fill="class",x=NULL, y=NULL, title="Pie Chart of Vegetation", caption="Source: Worms")