[R-sig-Geo] zip code map - huge files!

[Dylan Beaudette]

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 <h.wickham at gmail.com> 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 <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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>>
>
>
>
> --
> http://had.co.nz/
>
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