Venn diagram written in ggplot

ggvenn.R

library(ggplot2)
library(ggforce)

ggvenn <- function(a, b, ga, gb, title="") {
   
    # Calculate area
    x.a <- length(a)
    x.b <- length(b)
    x.u <- length(intersect(a, b))
    
    # Normalize area between 0-1
    nx.a <- x.a/(x.a+x.b)
    nx.b <- x.b/(x.a+x.b)
    
    # Circle radius and diameter
    r.a <- sqrt(nx.a/pi); d.a <- r.a*2
    r.b <- sqrt(nx.b/pi); d.b <- r.b*2
    
    ol <- ifelse(x.a < x.b, d.a*x.u/x.a, d.b*x.u/x.b)
    
    data.frame(x=c(-r.b-r.a+ol, 0), y=c(0, 0),
               groups=c(paste(ga, ' (', x.a, ')', sep=''),
                        paste(gb, ' (', x.b, ')', sep=''))) %>%
        
    ggplot(aes(x0=x, y0=y, r=c(r.a, r.b), fill=groups)) +
    ggtitle(title) +
    geom_circle(alpha=0.3, size = 0.5) +
    coord_fixed() +
    theme_void() +
    theme(plot.title = element_text(hjust = 0.5))
}