Sunday, September 30, 2012

Plot R Data With googleVis

Here is a little code snippet that shows how to do two things

  1. Use the Google Maps API to resolve place names into lat-long coordinate pairs.
  2. Plot R dataframes that contain lat-long data (for example from #1) onto Google Maps for quick visualization using the googleVis package.  The embedded map looks a little wonky here but it looks perfectly normal when you plot it locally in your browser. (Note: you need an internet connection for these maps to plot properly). 
Data: plotData • Chart ID: MapID71b85742e7
R version 2.14.1 (2011-12-22) • googleVis-0.2.15Google Terms of UseData Policy
####functions borrwed from
getDocNodeVal=function(doc, path)
   sapply(getNodeSet(doc, path), function(el) xmlValue(el))
  doc = xmlTreeParse(u, useInternal=TRUE)
  str=gsub(' ','%20',str)
  lat=getDocNodeVal(doc, "/GeocodeResponse/result/geometry/location/lat")
  lng=getDocNodeVal(doc, "/GeocodeResponse/result/geometry/location/lng")
  list(lat = lat, lng = lng)
#### End functions borrowed from
# get some names of paleoanthropological sites in France. 
placeNames<-c("Cro Magnon","La Ferrassie","Chauvet Cave","La Chapelle aux Saints", "Le Moustier")
#resolve the placenames into latlong
latLong<-lapply(placeNames, FUN=gGeoCode)
#format the latlong coordinates into the proper format lat:long
#create a dataframe, formatting the place name string first and making the latlong a vector, not list
sites<-gvisMap(plotData,locationvar="latlong",tipvar="name", options=list(mapType='normal'))
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