Hi, You can use the v.generalize command in GRASS to reduce the complexity of vectors like these.
Cheers, Dylan On Sun, Apr 26, 2009 at 3:53 PM, hadley wickham <[email protected]> wrote: > 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 <[email protected]> > 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 >> >> _______________________________________________ >> R-sig-Geo mailing list >> [email protected] >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> > > > > -- > http://had.co.nz/ > > _______________________________________________ > R-sig-Geo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
