On 11/01/2010 09:53 PM, Muenchen, Robert A (Bob) wrote:
> Hi All,
>
> I'm having great fun learning the vast array of mapping options in R. I'm now
> working on a teaching example (below) that will step slowly through creating
> a tiny map, converting it to SpatialPolygons and then plotting a choropleth
> and bubble plots in several ways (to be simplified to just one way when I'm
> done learning.)
>
> The first place I'm stuck is getting a legend to handle both size and color
> at the same time on the bubble plot (2nd from bottom). Either one works by
> itself, but not both together.
>
> My second problem is using plot twice with "add=TRUE" (bottom example). When
> I run the book example though it works fine, so I've got to be doing
> something truly inane.
>
> Finally, I'm plotting the bubbles in the centers of the regions that I
> entered into a dataframe. That seems silly since these are created
> automatically when I convert from a map object to a SpatialPolygons object,
> and stored in the labpt slots. There must be an easy way to call them from
> there, but I haven't figured it out.
>
> Thanks!
> Bob
>
> Here's what I've got so far:
>
> #----------------------------------------
> # Create a "map" class object of Tinyland
> #----------------------------------------
> long <- c(
> 20, 25, 32, 30, 27, 18, 20, NA,
> 35, 42, 42, 32, 25, 29, 35, NA,
> 30, 35, 35, 29, 25, 20, 20, 24, 30)
> lat <- c(
> 30, 30, 35, 39, 39, 34, 30, NA,
> 21, 25, 33, 35, 30, 23, 21, NA,
> 18, 18, 21, 23, 30, 30, 25, 20, 18)
> range <- c(18, 42, 18, 39)
> names=c("A","B","C")
> TinylandMap <- list(
> x=long,
> y=lat,
> names=names,
> range=range)
> class(TinylandMap) <- "map"
>
> TinylandMap
> map(TinylandMap)
>
> # Now convert it to a SpatialPolygon object
>
> library("maptools")
> TinylandSP <- map2SpatialPolygons( TinylandMap,
> IDs=TinylandMap$names,
> proj4string=CRS("+proj=longlat +ellps=WGS84") )
> str(TinylandSP, max.level=2)
> plot(TinylandSP)
>
> # Create some "pop"ulation data
> region <- c("A","B","C")
> pop <- c(271828, 314159, 195996)
> labptX <- c(25,34,26) #X-value of center of each region
> labptY <- c(34,28,23) #Y-value of center of each region
> myPopData <- data.frame(region,labptX,labptY,pop)
> myPopData
>
> # Get some grey shades
> # could automate this: myGreys <- grey( (1-( pop / max(pop) ) ) )
> # but these look nicer:
> myGreys <- c("gray60","gray30","gray90")
> myGreys
>
> # Choroploth plot from SpatialPolygons
> plot(TinylandSP, col = myGreys )
> legend( 37, 38 ,
> pop,
> fill = myGreys )
> text( 37, 38.5, pos=4, "pop")
>
> # Create some Character EXpansion values
> myCexValues <- 5*pop/max(pop)
>
> # This works and has a nice legend:
> library(PBSmapping)
> plot(TinylandSP)
> addBubbles(labptX, labptY, pop,
> legend.type="nested", col="grey")
>
> # This almost works but legend bubbles are not black
> # and overlap quite a bit. Is the legend function
> # capable of making the points black?
>
> plot(TinylandSP)
> symbols(labptX, labptY, circles=pop, inches=1/5, bg="black", add=TRUE)
> legend( 37, 38, legend=pop,
> pch=1, pt.cex=myCexValues)
use
pch = 16, y.intersp=2
in the legend command.
> # Here I'm trying to follow the example from
> # Applied Spatial Data Analysis with R
> # page 67 bottom by using plot twice.
> # But the 2nd plot says "add is not a graphical parameter"
> # so the bubbles start over on a blank map
> # I'm also trying fill="black" in the legend & getting squares
>
> plot(TinylandSP)
> plot( labptX, labptY, pch=1, bg="black", cex=myCexValues, add=TRUE )
> legend( "topright", legend=pop,
> pch=1, pt.cex=myCexValues, fill="black")
instead of the second plot, use:
points(labptX, labptY, pch=1, bg="black", cex=myCexValues)
>
> =========================================================
> Bob Muenchen (pronounced Min'-chen), Manager
> Research Computing Support
> Voice: (865) 974-5230
> Email: muenc...@utk.edu
> Web: http://oit.utk.edu/research,
> News: http://oit.utk.edu/research/news.php
> ========================================================
>
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--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics e.pebe...@wwu.de
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