RgoogleMaps (version 1.1.9.3)

PlotPolysOnStaticMap: plots polygons on map

Description

This function plots/overlays polygons on a map. Typically, the polygons originate from a shapefile.

Usage

PlotPolysOnStaticMap(MyMap, polys, col, TrueProj = TRUE, verbose = 1, ...)

Arguments

MyMap

map image returned from e.g. GetMap()

polys

polygons to overlay

col

(optional) vector of colors, one for each polygon

TrueProj

set to FALSE if you are willing to accept some degree of inaccuracy in the mapping. In that case, the coordinates of the image are in lat/lon and the user can simply overly points/lines/axis without worrying about projections

verbose

level of verbosity

...

further arguments passed to PlotOnStaticMap

Value

See Also

PlotOnStaticMap mypolygon

Examples

require(PBSmapping);
  shpFile <- paste(system.file(package = "RgoogleMaps"), "/shapes/bg11_d00.shp", sep = "")
  #shpFile <- system.file('bg11_d00.shp', package = "RgoogleMaps");
  
  shp=importShapefile(shpFile,projection="LL");
  bb <- qbbox(lat = shp[,"Y"], lon = shp[,"X"]);
  MyMap <- GetMap.bbox(bb$lonR, bb$latR, destfile = "DC.jpg");
  PlotPolysOnStaticMap(MyMap, shp, lwd=.5, col = rgb(0.25,0.25,0.25,0.025), add = F);

  #North Carolina SIDS data set:
  shpFile <- system.file("shapes/sids.shp", package="maptools");
  shp=importShapefile(shpFile,projection="LL");
  bb <- qbbox(lat = shp[,"Y"], lon = shp[,"X"]);
  MyMap <- GetMap.bbox(bb$lonR, bb$latR, destfile = "SIDS.jpg");
  #compute regularized SID rate
  sid <- 100*attr(shp, "PolyData")$SID74/(attr(shp, "PolyData")$BIR74+500)
  b <- as.integer(cut(sid, quantile(sid, seq(0,1,length=8)) ));
  b[is.na(b)] <- 1;
  opal <- col2rgb(grey.colors(7), alpha=TRUE)/255; opal["alpha",] <- 0.2;
  shp[,"col"] <- rgb(0.1,0.1,0.1,0.2);
  for (i in 1:length(b)) 
    shp[shp[,"PID"] == i,"col"] <- rgb(opal[1,b[i]],opal[2,b[i]],opal[3,b[i]],opal[4,b[i]]);
  PlotPolysOnStaticMap(MyMap, shp, lwd=.5, col = shp[,"col"], add = F);
  
  #compare the accuracy of this plot to a Google Map overlay:
  library(maptools);
  qk <- SpatialPointsDataFrame(as.data.frame(shp[, c("X","Y")]), as.data.frame(shp[, c("X","Y")]))
  proj4string(qk) <- CRS("+proj=longlat");
  tf <- "NC.counties";
  SGqk <- GE_SpatialGrid(qk)
  png(file=paste(tf, ".png", sep=""), width=SGqk$width, height=SGqk$height,
  bg="transparent")
  par(mar=c(0,0,0,0), xaxs="i", yaxs="i");par(mai = rep(0,4))
  plotPolys(shp, plt=NULL)
  dev.off()
  kmlOverlay(SGqk, paste(tf, ".kml", sep=""), paste(tf, ".png", sep=""));
  #This kml file can now be inspected in Google Earth or Google Maps
  
  #or choose an aspect ratio that corresponds better to North Carolina's elongated shape:
  MyMap <- GetMap.bbox(bb$lonR, bb$latR, destfile = "SIDS.jpg", size = c(640, 320), zoom = 7);
  PlotPolysOnStaticMap(MyMap, shp, lwd=.5, col = shp[,"col"], add = F);