R: plot circular histograms/rose diagrams on map

Question

I am trying to plot rose diagrams/ circular histograms on specific coordinates on a map analogous to drawing pie charts on a map as in the package mapplots.

Below is an example generated with mapplots (see below for code), I'd like to replace the pie charts with rose diagrams

The package circular lets me plot the rose diagrams, but I am unable to integrate it with the mapplots package. Any suggestions for alternative packages or code to achieve this?

In response to the question for the code to make the map. It's all based on the mapplots package. I downloaded a shapefile for the map (I think from http://www.freegisdata.org/)

library(mapplots)
library(shapefiles)

xlim = c(-180, 180)
ylim = c(-90, 90)

#load shapefile
wmap = read.shapefile ("xxx")

# define x,y,z for pies
x <- c(-100, 100)
y <- c(50, -50)
z1 <- c(0.25, 0.25, 0.5)
z2 <- c(0.5, 0.2, 0.3)
z <- rbind(z1,z2)
# define radii of the pies
r <- c(5, 10)

# it's easier to have all data in a single df

plot(NA, xlim = xlim, ylim = ylim, cex = 0.75, xlab = NA, ylab = NA)
draw.shape(wmap, col = "grey", border = "NA")
draw.pie(x,y,z,radius = r, col=c("blue", "yellow", "red"))
legend.pie (x = -160, y = -70, labels = c("0", "1", "2"), radius = 5,
bty = "n", cex = 0.5, label.dist=1.5, col = c("blue", "yellow", "red"))

the legend for the pie size can then be added using legend.bubble

Answer 1

Have a look at this example, you can use the map as background an plot your rose diagrams withPlotrix or ggplot2. In either case you would want to overlay multiple of these diagrams on top of your map which is easy to do in ggplot, just have a look at the example.

Answer 2

I discovered subplot() in the package Hmisc, which seems to do exactly what I wanted. Below is my solution (without the map in the background, which can be plotted using mapplots). I am open to suggestions on how to improve this though...

library(Hmisc)
library (circular)

dat <- data.frame(replicate(2,sample(0:360,10,rep=TRUE)))
lat <- c(50, -40)
lon <- c(-100, 20)

# convert to class circular
cir.dat <- as.circular (dat, type ='angles', units = 'degrees', template = 'geographic', modulo = 'asis', zero = 'pi/2', rotation = 'clock')

# function for subplot, plots relative frequencies, see rose.diag for how to adjust the plot
sub.rose <- function(x){
                nu <- sum(!is.na(x))
                de <- max(hist(x, breaks = (seq(0, 360, 30)), plot = FALSE)$counts)
                prop <- nu/de
                rose.diag(x, bins = 12, ticks = FALSE, axes = FALSE,
                radii.scale = 'linear',
                border = NA, 
                prop = prop,
                col = 'black'
                )
                }

plot(NA, xlim = xlim, ylim = ylim)
for(i in 1:length(lat)){
    subplot(sub.rose(cir.dat[,i]), x = lon[i], y = lat[i], size = c(1, 1))
    }