Create and write a KML file on the basis of a given Polygons object

Description

The function is used to create and write a KML file on the basis of a given Polygons object (a list of Polygon objects) for the usage in Google Earth resp. Google Maps.

Usage

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kmlPolygon(obj=NULL, kmlfile=NULL, 
    name="R Polygon", description="", col=NULL, visibility=1, lwd=1, border=1,
    kmlname="", kmldescription="")

Arguments

obj

a Polygons or SpatialPolygonsDataFrame object

kmlfile

if not NULL the name as character string of the kml file to be written

name

the name of the KML polygon

description

the description of the KML polygon (HTML tags allowed)

col

the fill color (see also Color Specification) of the KML polygon

visibility

if set to 1 or TRUE specifies that the KML polygon should be visible after loading

lwd

the stroke width for the KML polygon

border

the stroke color (see also Color Specification) for the KML polygon

kmlname

the name of the KML layer

kmldescription

the description of the KML layer (HTML tags allowed)

Details

The function is used to convert a given Polygons object (a list of Polygon objects) or the first Polygons object listed in a passed SpatialPolygonsDataFrame object into KML polygon. If kmlfile is not NULL the result will be written into that file. If kmlfile is NULL the generated KML lines will be returned (see also value).

The conversion can also handle polygons which are marked as holes inside of the Polygons object if these holes are listed right after that polygon in which these holes appear. That implies that a given plot order set in the Polygons object will not be considered.

For a passed Polygons object the function generates a <Style> tag whereby its id attribute is set to the passed object's ID.

Note that the geometries should be in geographical coordinates with datum WGS84.

The resulting KML polygon will be embedded in <Placemark><MultiGeometry><Polygon>.

Value

x is a list with the elements style and content containing the generated lines of the KML file as character vectors if kmlfile is NULL.

y is a list with the elements header and footer representing the KML file' header resp. footer if obj is NULL (see second example).

Color Specification

The following color specifications are allowed: 'red', 2, or as hex code '#RRGGBB' resp. '#RRGGBBAA' for passing the alpha value.

Author(s)

Hans-J. Bibiko

See Also

kmlOverlay, kmlLine, SpatialPolygons

Examples

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data(wrld_simpl)
## creates a KML file containing the polygons of South Africa (plus hole)
sw <- slot(wrld_simpl[wrld_simpl$NAME=="South Africa",], "polygons")[[1]]
tf <- tempfile()
kmlPolygon(sw, kmlfile=tf, name="South Africa", col="#df0000aa", lwd=5, 
    border=4, kmlname="R Test", 
    kmldescription="This is <b>only</b> a <a href='http://www.r-project.org'>R</a> test.")
tf

## creates a KML file containing the polygons of South Africa, Switzerland, and Canada
sw  <- wrld_simpl[wrld_simpl$NAME %in% c("South Africa", "Switzerland", "Canada"),]
out <- sapply(slot(sw, "polygons"), function(x) { kmlPolygon(x,
    name=as(sw, "data.frame")[slot(x, "ID"), "NAME"], 
    col="red", lwd=1.5, border='black', 
    description=paste("ISO3:", slot(x, "ID"))) })
tf <- tempfile()
kmlFile <- file(tf, "w")
tf
cat(kmlPolygon(kmlname="R Test", kmldescription="<i>Hello</i>")$header, 
    file=kmlFile, sep="\n")
cat(unlist(out["style",]), file=kmlFile, sep="\n")
cat(unlist(out["content",]), file=kmlFile, sep="\n")
cat(kmlPolygon()$footer, file=kmlFile, sep="\n")
close(kmlFile)

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