zip code map - huge files!
Hi Enrico, I have some code to do map generalisation (reducing map resolution without visible loss in detail) at http://github.com/hadley/data-counties/tree/master. It's applied to counties data, but would be trivial (if slow) to modify to work with zip codes instead Hadley
On Sun, Apr 26, 2009 at 3:06 PM, Enrico Rossi <enrico.a.rossi at gmail.com> wrote:
Hello, I have some data at the zip code level, and I'm using the shapefiles downloaded from the Census TigerLine website (http://www2.census.gov/geo/tiger/TIGER2008/tl_2008_us_zcta5.zip) to plot a shaded map of the US. However, the files generated in this way are enormous, and take a long time to process, even on a fast machine with lots of memory. I'm wondering if there's a more efficient way to do this. Maybe rasterize before plotting somehow? If anyone on this list has experience working with zip-level data, I'd appreciate any advice. Here's some example code like what I'm doing: # This works, and produces a 1.2GB PDF file! After it's done, I can rasterize it using gs to reduce file size, but it takes almost an hour library(maptools) zip<-readShapePoly("tl_2008_us_zcta5") ?# This takes a while! val<-runif(length(zip[[1]])) # there are about 32000 zip codes pdf("zipplot.pdf") plot(zip,xlim=c(-130,-65),ylim=c(20,50),col=grey(val),lty=0) dev.off() system("gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r300 -dTextAlphaBits=4 -dGraphicsAlphaBits=4 -dMaxStripSize=8192 -sOutputFile=zipplot.png zipplot.pdf") # I've tried plotting directly to png, but it just seems to hang, my patience ran out after two hours png("zipplot.png") plot(zip,xlim=c(-130,-65),ylim=c(20,50),col=grey(val),lty=0) dev.off() # This also takes too long, I never got any output out of it library(lattice) zip$val<-val pdf("zipplot2.pdf") spplot(zip,"val",xlim=c(-130,-65),ylim=c(20,50),lty=0) dev.off() Many thanks! Enrico Rossi
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