library(grid)
# Install this library if you don't have it already.

plot.hc <- function(mat){
  m <- dim(mat)[1]
  n <- dim(mat)[2]
  grid.newpage()
  rad = .02
  xx = function(j) {j/(n+1)}
  yy = function(i) {(m+1-i)/(m+1)}
  for(i in 1:m)grid.lines(c(xx(1),xx(n)),c(yy(i),yy(i)))
  for(j in 1:n)grid.lines(c(xx(j),xx(j)),c(yy(1),yy(m)))
  for(j in 1:n){
    for(i in 1:m){
      mycolor <- c('black','green')[1+mat[i,j]]
      grid.circle(xx(j),yy(i),rad,gp=gpar(fill=mycolor))
    }
  }
}

set.seed(3)
m <- 8
n <- 8
mat <- matrix(rbinom(m*n, 1, .2),m,n)
mat
plot.hc(mat)

# Note: the "mat" you just created does not satisfy the hard-core
# constraint; it is just an example to demonstrate the plot.hc function.