This won't show up To load and execute this code in R, you will need the XML package, and the following command 
doc = xmlTreeParse("http://www.omegahat.org/GoogleEarth/CityTemperatures/CityTemperatures.xml", useInternal = TRUE)
v = getNodeSet(doc, "//r:init|//r:code|//r:function", "r")
sapply(v, function(node) {  cmd = parse(text = xmlValue(node)); eval(cmd, globalenv())})
This merely finds all the relevant nodes and parses and evaluates them to emulate what source() does. We have a package that provides a function xmlSource that does this. We start by loading the XML library and defining some global variables that control the computations in function calls that create the KML document. library(XML) useStyle = TRUE If we already have the data, then there is no need to load it. Otherwise, we fetch it from the URL below. We also add a new variable which breaks the temperatures into four groups. if(!exists("temperature") || class(temperature) != "data.frame") { # This version has intentional errors. load(url("http://eeyore.ucdavis.edu/stat32/Data/Temperature.rda")) temperature$level = cut(temperature$temp, 4) } We will want to identify these four temperature groups by different colors and we use a rainbow color, with red corresponding to high values and blue/purple corresponding to colder values. # Generate some colors to use to represent the different levels of temperature temperatureColors = rev(rainbow(length(levels(temperature$level)))) A KML document starts with a "kml" node and then a Document sub-node. Note that we make the default namespace the Google Earth namespace. There is no name on this element in the vector, so it becomes the default namespace. # Create the KML document tt = xmlTree("kml", namespaces = c("http://earth.google.com/kml/2.1")) tt$addTag("Document", close = FALSE) We put a general description for the contents of the entire file which will be shown when the user clicks on the top-level node for this file in the Places panel. Note that the content can be HTML, and not just simple text. So we add a link to my web site. We could easily use other markup and insert images. We'll see that later. # Put a little HTML description of what we are displaying. tt$addTag("description", 'Illustrates the temperatures of 50 different cities at 4 different times of the year.\nGenerated from R by Duncan Temple Lang') We'd like to have a single place that controls how the labels on the points in the Placemarks are displayed, e.g. the color, the size and so on. We define a Style and give the attributes we want to control. In each Placemark element in the document, we can refer to this style so that it takes effect for that particular Placemark. We specify sub-elements for both the icon and the label styles. We specify a scale and a color. The colors are given in slightly different form than in R. There are four values giving alpha, blue, green and red. Each value is from 00 to FF in hexadecimal. 00 means transparent for the alpha blending. # A top-level, global style to which we can refer within Placemarks, etc. if(useStyle) { tt$addTag("Style", attrs = list(id = "me"), close = FALSE) tt$addTag("IconStyle", close = FALSE) tt$addTag("scale", .35) tt$addTag("color", "#FFFF0000") tt$closeNode() tt$addTag("LabelStyle", close = FALSE) tt$addTag("scale", 1) # note the alpha-blue-green-red order tt$addTag("color", "#FFFFFF00") tt$closeNode() tt$closeNode() } This is the function that does all the work to generate the content. 1) paste(row[1, "temp"], mnth) else row[1, "temp"] tt$addNode("name", label) if(showImages) { tt$addTag("IconStyle", close = FALSE) tt$addTag("Icon", close = FALSE) tt$addTag("href", imageName(city[1, "city"])) tt$closeNode() tt$closeNode() } else { tt$addNode("styleUrl", paste("#", style, sep = "")) } tt$addNode("TimeStamp", close = FALSE) tt$addNode("when", paste("1997", sprintf("%02d", match(mnth, month.name)), sep = "-")) #tt$closeNode() tt$closeNode() if(length(months) > 1) { # we don't need the table now that we have desc = list(name, "", c("", paste("", sep = ""), ""), c("", paste("", sep = ""), ""), "
", months, "
", city$temp, "
", c("")) desc = paste(sapply(desc, paste, collapse = ""), collapse = "\n") tt$addNode("description", close = FALSE) tt$addCData(desc) tt$closeNode() # description } else { desc = paste("Temperature for", city, row["temp"], "in", mnth) tt$addNode("description", desc) } tt$addNode("Point", close = FALSE) tt$addNode("coordinates", paste(- as.numeric(row["longitude"]), row["latitude"], sep = ", ")) tt$closeNode() # Point tt$closeNode() # Placemark # should be one closeTag(2) }) # Ground Overlay to show the time series curve of temperature across the 4 months. tt$addNode("GroundOverlay", close = FALSE) tt$addNode("name", city[1, "city"]) tt$addNode("Icon", close = FALSE) tt$addNode("color", "#88FFFFFF") tt$addTag("href", imageName(city[1, "city"])) tt$closeNode() tt$addNode("LatLonBox", close = FALSE) off = c(.5, .5)*3 loc = as.numeric(city[1, c("longitude", "latitude")]) box = c(north = loc[2] + off[2], south = loc[2] - off[2], east = -loc[1] + off[1], west = -loc[1] - off[1]) sapply(names(box), function(i) tt$addNode(i, box[i])) tt$closeNode() # LatLonBox tt$closeNode() # GroundOverlay tt$closeNode() # Folder }) ) } ]]> We now arrange to call this function. (Note that we had several different functions in an earlier version and we arranged them as functions so that we could easily control which one was invoked.) f() And finally, we want to place the legend on the screen. It is not tied to a particular longitude, latitude pair. Rather, it should be in the lower-left corner of the screen. So we use a ScreenOverlay element. We give a name so that users can identify it more readily in the Places tree. We specify the icon to display by giving the name of the file. And we specify its coordinates, using pixel units rather than proportions, etc. # Create the screen overlay that will display the legend in the lower left corner. # The legend should have no margins in R. tt$addNode("ScreenOverlay", close = FALSE) tt$addNode("name", "Temperature legend") tt$addNode("Icon", "legend.png") tt$addNode("screenXY", attrs = c("x" = 2, "y" = 2, xunits = "pixels", yunits = "pixels")) tt$addNode("overlayXY", attrs = c("x" = 0, "y" = 0)) tt$addNode("size", attrs = c("x" = 300, "y" = 300, xunits = "pixels", yunits = "pixels")) tt$closeNode() # ScreenOverlay And finally, we close the top-level kml node. (Is this actually the Document node? It doesn't really matter as we are not adding any more nodes so they don't have to be closed explicitly.) tt$closeNode() # KML root node And finally, we write this to a file and tell Google Earth to open it. This works on the Mac. On Windows, we could use DCOM and on Linux, we would use a slightly different approach which we have to work out soon. saveXML(tt, "/tmp/doc.kml") system("open /tmp/doc.kml") In order to be able to distribute the KML file and the associated images, we compress them into a single file system("zip /tmp/CityTemperatures.kmz /tmp/doc.kml /tmp/*.png")
Appendix Here we include the code that creates the images and manages the names of these images so that the functions that create the files and the code that references those files are synchornized and refer to the same file. This function computes the name of the file that will be used to store the image for the given city. This deals with prepending the directory if full is given and whether the file is for the image on the Google Earth display or in the popup window. imageName = function(city, full = FALSE, mini = FALSE, ext = "png") { id = gsub("[ ,]", "_", city) if(is.logical(full)) { if(full) id = paste("file://", getwd(), id, sep = .Platform$file.sep) } else id = paste(full, id, sep = .Platform$file.sep) if(mini) id = paste(id, "mini", sep = "_") id = paste(id, ext, sep = ".") id } This function creates the time-series plot for a given city. makeHist = function(z, device = png, ylim = range(z$temp), full = FALSE, mini = FALSE, cols = temperatureColors) { # cols = rainbow(length(levels(z$level))) id = imageName(z[1, "city"], full, mini = mini) if(!is.null(device)) { device(id, width = 300, height = 300, bg = "transparent") on.exit(dev.off()) } plot(z$temp, xlab = "", ylab = "", axes = FALSE, ylim = ylim, col = cols[z$level]) segments(1:3, z$temp[1:3], 2:4, z$temp[2:4], col = cols[z$level], lwd = if(mini) 2 else 30) axis(2) id } This is the function that we use to create the time series plots that appear on the Google Earth display. If mini is , then the plots for the balloon popup windows are created. This function creates a plot for each city. createHist = function(data = temperature, f = makeHist, full = "/tmp", mini = FALSE) { invisible(by(data, factor(data$city), f, ylim = range(data$temp), full = full, mini = mini)) } This function is used to create the legend that appears in the lower-left corner of the Google Earth screen. 0) { trellis.device(png, filename = filename, bg = "transparent") on.exit(dev.off()) } trellis.par.set(axis.text = list(col = "white", cex=1.2, font=2)) # print(simpleKey(levels(levels?dra), rectangles = list(TRUE, col = rainbow(4))) breaks = c(min(values$temp), by(values$temp, values$level, max)) k = list(at = breaks, labels = as.character(breaks), col= colors, width= key.width ) draw.colorkey(key = k, draw = TRUE, viewport(height = unit(.9, "npc"))) } ]]>