[R] How to add circular text for a graph with concentric circles

[sparandekar at worldbank.org]

Dear R experts,

I am plotting the population of students who live in a city, and in 
successive circular bands made of the contiguous districts that surround 
the city. This is a stylized figure, where I specify the area of each 
successive circle based on the cumulative population of students. I want 
to compare two sets of concentric circles across different populations - 
such as 'All students' and 'Private students' (those attending private 
school) by using the same colours and the same dimension of the outer 
circle. I have attached the .pdf file with the output, and the R code to 
generate the first set of circles.

I would appreciate any tips about how to rotate the text label that marks 
each concentric circle (except the central circle) to be curved around the 
circle, located in the middle of each band, thus following the circle 
instead of being horizontal, as I have it now.

Thank you very much,

best regards,
Suhas

# Conurbano1a.R
# R Program to generate circles, radii based on proportion of ALL STUDENTS
# Prepared by Suhas, Tuesday, July 24, 2007

grid.circle(x=0.5, y=0.5, r=3*(.1268), default.units="npc", name=NULL,
                 gp=gpar(fill="olivedrab1",col=NULL), draw=TRUE, vp=NULL)
grid.circle(x=0.5, y=0.5, r=3*(0.095882), default.units="npc", name=NULL,
                 gp=gpar(fill="cornflowerblue",col=NULL), draw=TRUE, 
vp=NULL)
grid.circle(x=0.5, y=0.5, r=3*(0.077894), default.units="npc", name=NULL,
                 gp=gpar(fill="aliceblue",col=NULL), draw=TRUE, vp=NULL)
grid.circle(x=0.5, y=0.5, r=3*(0.061884), default.units="npc", name=NULL,
                 gp=gpar(fill="seagreen",col=NULL), draw=TRUE, vp=NULL)
grid.circle(x=0.5, y=0.5, r=3*(0.050740), default.units="npc", name=NULL,
                 gp=gpar(fill="lightpink2",col=NULL), draw=TRUE, vp=NULL)
grid.circle(x=0.5, y=0.5, r=3*(0.045906), default.units="npc", name=NULL,
                 gp=gpar(fill="navy",col=NULL), draw=TRUE, vp=NULL)

# Now to add the labels ? used trial and error for x and y values

  grid.text("Provincia Interior", x=0.5, y=0.85,
               gp=gpar(fontsize=6, col="black"))

  grid.text("Conurbano 4", x=0.5, y=0.75,
               gp=gpar(fontsize=6, col="black"))

  grid.text("Conurbano 3", x=0.5, y=0.71,
               gp=gpar(fontsize=6, col="black"))

  grid.text("Conurbano 2", x=0.5, y=0.67,
               gp=gpar(fontsize=6, col="white"))

  grid.text("Conurbano 1", x=0.5, y=0.645,
               gp=gpar(fontsize=6, col="black"))
  grid.text("Ciudad de Buenos Aires", x=0.5, y=0.56,
               gp=gpar(fontsize=6, col="white"))

# Title of graph 
grid.text("All Students", x=0.2,y=0.95,gp=gpar(fontsize=20,col="navy"))




**************************************************************************
Suhas D. Parandekar
Senior Education Economist
Latin American and Caribbean Region
Tel: 202 458 7622
e-mail: sparandekar at worldbank.org