dotRData

library(ggplot2)
library(data.table)

ggplot(data.table(x=c(-2, 2)), aes(x)) + 
  stat_function(fun=function(x) sqrt(1 - (abs(x)-1)^2), color='red', size=3) +
  stat_function(fun=function(x) -3*sqrt(1 - (sqrt(abs(x))/sqrt(2))), color='red', size=3) +
  theme(legend.position  = "none",
        panel.background = element_rect(fill = "black"),
        axis.ticks       = element_blank(),
        panel.grid       = element_blank(),