[R-sig-Geo] bitmap plots in loop

[Takatsugu Kobayashi]

hi,

I have read a couple of threads about png and jpg not being supported in 
R CMD BATCH. So I decided to use bitmap() instead. I would like to 
repeat printing jobs 1000 times. I only got empty png files. Doesn't 
this loop open bitmap, plot, close bitmap everytime?

rm(list=ls(all=T))

### Include necessary packages
library(sp)
library(maptools)

pts <- c(2,3,4,5,6,7,8,9,10)
for (iter in 1:length(pts))
{
### Define parameters for a grid
start.point <- -pts
cco <- c(start.point,start.point)
csize <- c(1,1)
n <- abs(cco[1]*2)+1
cnum <- c(n,n)
grd <- GridTopology(cco, csize, cnum)
r.grd <- as(grd, "SpatialPolygons")

### Assign some values to grid cells
ID <- sapply(slot(r.grd, "polygons"), function(x) slot(x, "ID"))
resdf <- data.frame(com.time=runif(n^2), row.names=ID)
r.grd.df <- SpatialPolygonsDataFrame(r.grd, resdf)

### save bitmap images s
bitmap(file=paste('output/gridcell',iter,'_new.png',sep=''),type='png256', 
width=5, height=5)
spplot(r.grd.df)
dev.off()
}

I appreciate your help.

Taka