Happy 4th of July!

july4.R

library(plyr)
library(ggplot2)

# from: http://www.codeproject.com/Articles/18149/Draw-a-US-Flag-using-C-and-GDI
star_coords <- function(x, y, r, r1){
  a <- 72 * pi /180
  b <- a/2
  df <- data.frame(
    x = x + c(0, r1*sin(b), r*cos(pi/2 - a), r1*cos(a + b - pi/2), r*sin(b),
      0, -r*sin(b), -r1*cos(a + b - pi/2), - r*cos(pi/2 - a), -r1*sin(b)), 
    y = y + c(r, r1*cos(b), r*sin(pi/2 - a), -r1*sin(a + b - pi/2), -r*cos(b),
      -r1,  -r*cos(b), -r1*sin(a + b - pi/2), r*sin(pi/2 - a), r1*cos(b)))
}
stars_cents <-  expand.grid(
  x = seq(0.063, 0.76 - 0.063, 0.063),
  y = 1 - seq(0.054, 7/13, 0.054))[c(TRUE, FALSE), ]

stars <- mdply(stars_cents, star_coords, r = 0.0616/2, r1 = 0.38*0.0616/2)
stars$group <- rep(1:nrow(stars_cents), each = 10)
  
stripes <- data.frame(xmin = 0, xmax = 1.9, 
  ymin = seq(0, 1-1/13, 2/13), ymax = seq(1/13, 1, 2/13),
  fill = "#B22234")
union <- data.frame(xmin = 0, xmax = 0.76, 
  ymin = 1 - 7/13, ymax = 1, fill = "#3C3B6E")

print(ggplot(mapping = aes(xmin = xmin, xmax = xmax, 
       ymin = ymin, ymax = ymax, fill = fill)) +
  geom_rect(data = stripes) +
  geom_rect(data = union) +
  geom_polygon(aes(x = x, y = y, group = group), data = stars, fill = "white",
    inherit.aes = FALSE) +
  scale_fill_identity() +
  scale_shape_identity() +
  scale_y_continuous("", limits = c(0,1), expand = c(0,0)) +
  scale_x_continuous("", limits = c(0,1.9), expand = c(0,0)) +
  coord_equal()  + 
  theme(panel.background = element_rect(fill = "white"),
    axis.text = element_blank(),
    axis.ticks = element_blank()))