ggplot2 using facet_grid to generate Pie charts for each row

Question

I am trying to generate pie charts for this data.frame where each row represents a unique identifier for a site, the errors count for the fields and the, number of fields. How best would I structure the the ggplot command to produce a pie chart with errors being a fraction of the the fields for each site? Currently, my code looks like the following:

ggplot(error_indicator,aes(x = Fields,y=Errors)) 
+ facet_grid(~Hospital) 
+ geom_bar(width = 1,stat="identity", position="fill") 
+ coord_polar(theta="y")

The dataframe looks like the following:

But the result from my ggplot code looks like the following:

How do I get the pie charts to show errors as ratios of the fields for each hospital and each hospital using its own row?

Answer 1

First, pie charts is not the best way to show your data!

But anyway here is one solution. Most important part here is scale_y_continuous() to set limits from 0 to 1 and then convert them to percents using percent_format() from library scales.

library(ggplot2)
library(scales)
ggplot(df,aes(x=1,y=Errors/Fields))+geom_bar(stat="identity")+
  facet_grid(~Hospital)+
  coord_polar(theta="y")+
  scale_y_continuous(labels = percent_format(),limits=c(0,1),
              breaks=c(0.25,0.5,0.75,1))+
  theme(axis.title.y=element_blank(),
        axis.text.y=element_blank(),
        axis.ticks.y=element_blank())