Draw Regular Polygon(s)

Draw a regular polygon with n corners. This is the workhorse function for drawing regular polygons. Drawing a circle can be done by setting the vertices to a value of say 100. 

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)

Arguments

x, y

a vector (or scalar) of xy-coordinates of the center(s) of the regular polygon(s).

radius.x

a scalar or a vector giving the semi-major axis of the ellipse for the polygon(s).

radius.y

a scalar or a vector giving the semi-minor axis of the ellipse for the polygon(s). Default is radius.x which will result in a polygon with radius.x.

rot

angle of rotation in radians.

nv

number of vertices to draw the polygon(s).

border

color for borders. The default is par("fg"). Use border = NA to omit borders.

col

color(s) to fill or shade the shape with. The default NA (or also NULL) means do not fill (say draw transparent).

lty

line type for borders and shading; defaults to "solid".

lwd

line width for borders and shading.

plot

logical. If TRUE the structure will be plotted. If FALSE only the points are calculated and returned. Use this if you want to combine several geometric structures to a polygon.

Details

All geometric arguments will be recycled.

Value

The function invisibly returns a list of the calculated coordinates for all shapes.

Author

Andri Signorell <andri@signorell.net>

Examples

# 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)