How to create/enhance my own radar/polar chart without additional packages in R?-CodePudding

I've been trying to create a combination of radar/polar chart of a given vector of polygon vertices, without packages, but just with base R, which I really struggle with. So far, with some help, I have reached the following point:

a <- a <- abs(rnorm(5, mean = 4, sd = 2))
names(a) <- LETTERS[1:5]
stars(matrix(a,nrow=1),axes=TRUE, scale=FALSE,col.lines="blue",radius=FALSE)
center <- c(x=2.1, y=2.1) #the starchart for some reason chooses this as a center
half <- seq(0, pi, length.out = 51)
angle=45
for (D in a) {
  Xs <- D * cos(half); Ys <- D * sin(half)
  lines(center["x"]   Xs, center["y"]   Ys, col = "gray", xpd = NA, lty="dashed")
  lines(center["x"]   Xs, center["y"] - Ys, col = "gray", xpd = NA, lty="dashed")
}

which gives me something this:

What I would need to take further is:

center this mixed radar/polar chart at (0,0) and mark the center
color the polygon area transparently
add radii starting from the outermost circle and reaching the center through the polygon vertices
put the vector name labels on the ends of the radii on the outermost circle

So, the final result should look something like this:

I have experimented with the polygon(), symbols() functions and par() graphic parametres, but I am really struggling to combine them...My problem is that I don't understand how the stars() function plot coordinates selection relates to my input.

CodePudding user response：

Did not liked the stars functions... so I made a full rondabout with polygon:

polar_chart <- function(values){
  k <- length(values)
  m <- max(values)
  # initialise plot
  plot(1, type="n", xlab="", ylab="", xlim=1.2*m*c(-1,1), ylim=1.2*m*c(-1,1))
  # radial lines & letters
  sapply(k:1, function(x){
    text(1.1*m*cos(-(x-1)*2*pi/k   2*pi/3), 1.1*m*sin(-(x-1)*2*pi/k   2*pi/3),
         LETTERS[x], cex = 0.75)
    lines(c(0, m*cos((x-1)*2*pi/k   2*pi/3)), c(0, m*sin((x-1)*2*pi/k   2*pi/3)),
          col = "grey",lty="dashed")
    })
  # circles
  aux <- seq(2*pi   0.1, 0, -0.1)
  sapply(values, function(x) lines(x*cos(aux), x*sin(aux), col = "grey",lty="dashed"))
  # polygon
  x <- values*cos(-(1:k-1)*2*pi/k   2*pi/3)
  y <- values*sin(-(1:k-1)*2*pi/k   2*pi/3)
  polygon(c(x, x[1]),c(y, y[1]), col = "red", border = "blue", density = 50)
}

values <- abs(rnorm(5, mean = 4, sd = 2))
polar_chart(values)

And returns a plot like the following: