Converting bar chart to pie chart in R - r

Question

I have following data and code:
dd
grp categ condition value
1 A X P 2
2 B X P 5
3 A Y P 9
4 B Y P 6
5 A X Q 4
6 B X Q 5
7 A Y Q 8
8 B Y Q 2
>
>
dput(dd)
structure(list(grp = structure(c(1L, 2L, 1L, 2L, 1L, 2L, 1L,
2L), .Label = c("A", "B"), class = "factor"), categ = structure(c(1L,
1L, 2L, 2L, 1L, 1L, 2L, 2L), .Label = c("X", "Y"), class = "factor"),
condition = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L), .Label = c("P",
"Q"), class = "factor"), value = c(2, 5, 9, 6, 4, 5, 8, 2
)), .Names = c("grp", "categ", "condition", "value"), out.attrs = structure(list(
dim = structure(c(2L, 2L, 2L), .Names = c("grp", "categ",
"condition")), dimnames = structure(list(grp = c("grp=A",
"grp=B"), categ = c("categ=X", "categ=Y"), condition = c("condition=P",
"condition=Q")), .Names = c("grp", "categ", "condition"))), .Names = c("dim",
"dimnames")), row.names = c(NA, -8L), class = "data.frame")
ggplot(dd, aes(grp,value, fill=condition))+geom_bar(stat='identity')+facet_grid(~categ)
How can I convert this bar chart to pie chart? I want 4 pies here with their sizes corresponding to heights of respective bars here. I tried following but they did not work:
ggplot(dd, aes(grp,value, fill=condition))+geom_bar(stat='identity')+facet_grid(~categ)+coord_polar()
ggplot(dd, aes(grp,value, fill=condition))+geom_bar(stat='identity')+facet_grid(~categ)+coord_polar('y')
I also tried to make pie chart similar to Pie charts in ggplot2 with variable pie sizes but I am not able to manage with my data. Thanks for your help.

Answer 1

Using the same idea as in the link you posted, you could add a column size do your dataframe that would be the sum of the values for each group, and use that as the width argument:
library(dplyr)
dd<-dd %>% group_by(categ,grp) %>% mutate(size=sum(value))
ggplot(dd, aes(x=size/2,y=value,fill=condition,width=size))+geom_bar(position="fill",stat='identity')+facet_grid(grp~categ)+coord_polar("y")

Answer 2

You want the group and category both to be variables for the grid, and not inside any plot. Here are two different layouts. X ought to be any single item, string, or something else.
ggplot(dd, aes(x=factor(1),y=value,
fill=condition))+geom_bar(stat='identity')+
facet_grid(~grp+categ)+coord_polar("x")
ggplot(dd, aes(x=factor(1),y=value,
fill=condition))+geom_bar(stat='identity')+
facet_grid(grp~categ)+coord_polar("x")
Something strange happened with the top opening here, maybe its just my interface. Should get you going enough though!