DrawRegPolygon(x = 0, y = x, radius.x = 1, radius.y = radius.x, rot = 0,
            nv = 3, border = par("fg"), col = par("bg"), lty = par("lty"),
            lwd = par("lwd"), plot = TRUE)

# Draw 4 triangles (nv = 3) with different rotation angles
plot(c(0,1),c(0,1), asp=1, type="n", xaxt="n", yaxt="n", xlab="", ylab="")
DrawRegPolygon(x = 0.5, y = 0.5, rot = (1:4)*pi/6, radius.x = 0.5, nv = 3,
  col = SetAlpha("yellow",0.5))


# Draw several polygons
plot(c(0,1),c(0,1), asp=1, type="n", xaxt="n", yaxt="n", xlab="", ylab="")
DrawRegPolygon(x = 0.5, y = 0.5, radius.x=seq(50, 5, -10) * 1 /100,
  rot=0, nv = c(50, 10, 7, 4, 3), col=SetAlpha("blue",seq(0.2,0.7,0.1)))


# Combine several polygons by sorting the coordinates
# Calculate the xy-points for two concentric pentagons
d.pts <- do.call("rbind", lapply(DrawRegPolygon(radius.x=c(1,0.38), nv=5,
  rot=c(pi/2, pi/2+pi/5), plot=FALSE ), data.frame))

# prepare plot
plot(c(-1,1),c(-1,1), asp=1, type="n", xaxt="n", yaxt="n", xlab="", ylab="")

# .. and draw the polygon with reordered points
polygon( d.pts[order(rep(1:6, times=2), rep(1:2, each=6)), c("x","y")], col="yellow")



# Move the center
plot(c(0,1),c(0,1), asp=1, type="n", xaxt="n", yaxt="n", xlab="", ylab="")
theta <- seq(0, pi/6, length.out=5)
xy <- PolToCart( exp(theta) /2, theta)
DrawRegPolygon(x=xy$x, y=xy$y + 0.5, radius.x=seq(0.5, 0.1, -0.1),
  nv=4, rot=seq(0, pi/2, length.out=5), col=rainbow(5) )


# Plot a polygon with a "hole"
plot(c(-1,1),c(-1,1), asp=1, type="n", xaxt="n", yaxt="n", xlab="", ylab="")
DrawRegPolygon(nv = 4, rot=pi/4, col="red" )
text(x=0,y=0, "Polygon", cex=6, srt=45)

# Calculate circle and hexagon, but do not plot
pts <- DrawRegPolygon(radius.x=c(0.7, 0.5), nv = c(100, 6), plot=FALSE )

# combine the 2 shapes and plot the new structure
polygon(x = unlist(lapply(pts, "[", "x")),
  y=unlist(lapply(pts, "[", "y")), col="green", border=FALSE)