R GIS: Function to Reverse KML Paths
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Join For FreeThis is a function I wrote up for reversing KML-paths. The paths within a KML can partially matched by their name-tags.
## name: ReverseKmlPath ## use: Reverser a KML-path by matching its ## arguments: PATH_TO_DOC the path to the KML-file ## NAME the value of the name tag, function uses partial matching! ## 'Trail_xyz' will be matched by 'Trail' ## requirements: KML-structure with Placemarks containing a <name> and a <coordinates> tag ## author: Kay Cichini ## date: 01-05-2014 ## license: CC-BY-NC-SA ReverseKmlPath <- function(PATH_TO_DOC, NAMES) { require(XML) doc <- xmlInternalTreeParse(PATH_TO_DOC) if (xmlNamespaceDefinitions(doc)[[1]]$uri == "http://www.opengis.net/kml/2.2") { namespaces <- c(kml = "http://www.opengis.net/kml/2.2") flag <- 1 } else { if (xmlNamespaceDefinitions(doc)[[1]]$uri == "http://earth.google.com/kml/2.0") { namespaces <- c(kml0 = "http://earth.google.com/kml/2.0") flag <- 0 } else { stop ("Stopped!: Check namespace issue..") } } for (NAME in NAMES) { if (flag) { query <- paste0("//kml:Placemark[contains(kml:name,'", sprintf("%s", NAME), "'", ")]//kml:coordinates") } else { query <- paste0("//kml0:Placemark[contains(kml0:name,'", sprintf("%s", NAME), "'", ")]//kml0:coordinates") } coords <- tryCatch(getNodeSet(doc, query, namespaces), error = function(e) message(paste("\nError: *", NAME, "* was NOT successfully matched\n"))) for (i in length(coords)) { #grab coordinates from node and reverse order rev_coord_vector <- rev(unlist(strsplit(gsub("\\t|\\n", "", xmlValue(coords[[i]])), "\\s"))) rev_coord_string <- paste(rev_coord_vector, collapse = " ") # re-insert reversed line-string: xmlValue(coords[[i]]) <- rev_coord_string # message if (flag) { query <- paste0("//kml:Placemark[contains(kml:name,'", sprintf("%s", NAME), "'", ")]//kml:name") } else { query <- paste0("//kml0:Placemark[contains(kml0:name,'", sprintf("%s", NAME), "'", ")]//kml0:name") } match <- xmlValue(getNodeSet(doc, query, namespaces)[[i]]) message(paste0("matched name: ", match, "\n...")) } } # save: message("Reversed paths saved to:") saveXML(doc, paste0(dirname(PATH_TO_DOC), "/reversed_", basename(PATH_TO_DOC)), prefix = newXMLCommentNode("This file was created with the R-package XML::saveXML, see: ")) } ## not run: tf <- tempfile(fileext = ".kml") download.file("http://dev.openlayers.org/releases/OpenLayers-2.13.1/examples/kml/lines.kml", tf, mode = "wb") ReverseKmlPath( PATH_TO_DOC = tf, NAMES = c("Absolute", "Relative") ) shell.exec(tf) shell.exec(paste0(dirname(tf), "/reversed_", basename(tf))) </coordinates></name>
R (programming language)
Published at DZone with permission of Kay Cichini, DZone MVB. See the original article here.
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