how to draw two half circles in ggplot in r

Question

How can I make a plot like this with two different-sized half circles (or other shapes such as triangles etc.)?

I\'ve looked into a few options: Another pos

Answer 1

If you don't need to have ggplot2 map aesthetics other than x and y you could try egg::geom_custom,

# devtools::install_github("baptiste/egg")
library(egg)
library(grid)
library(ggplot2)

d = data.frame(r1= c(1,3,2), r2=c(3,6,5), x=1:3, y=1:3)
gl <- Map(mushroomGrob, r1=d$r1, r2=d$r2, gp=list(gpar(fill=c("bisque","maroon"), col="white")))
d$grobs <- I(gl)

ggplot(d, aes(x,y)) + 
  geom_custom(aes(data=grobs), grob_fun=I) +
  theme_minimal()

with the following grob,

mushroomGrob <- function(x=0.5, y=0.5, r1=0.2, r2=0.1, scale = 0.01, angle=0, gp=gpar()){
grob(x=x,y=y,r1=r1,r2=r2, scale=scale, angle=angle, gp=gp , cl="mushroom")
}

preDrawDetails.mushroom <- function(x){
  pushViewport(viewport(x=x$x,y=x$y))
}
postDrawDetails.mushroom<- function(x){
  upViewport()
}
drawDetails.mushroom <- function(x, recording=FALSE, ...){
  th2 <- seq(0,pi, length=180)
  th1 <- th2 + pi
  d1 <- x$r1*x$scale*cbind(cos(th1+x$angle*pi/180),sin(th1+x$angle*pi/180))
  d2 <- x$r2*x$scale*cbind(cos(th2+x$angle*pi/180),sin(th2+x$angle*pi/180))
  grid.polygon(unit(c(d1[,1],d2[,1]), "snpc")+unit(0.5,"npc"), 
              unit(c(d1[,2],d2[,2]), "snpc")+unit(0.5,"npc"),
              id=rep(1:2, each=length(th1)), gp=x$gp)
}



# grid.newpage()
# grid.draw(mushroomGrob(gp=gpar(fill=c("bisque","maroon"), col=NA)))