The "<observation ..." format of the tag tells us it's a [child] node in the document and the "//observation" XPath expression targets _all_ "observation" nodes (sometimes that's acceptable, sometimes you need to be more specific in the XPath expression you use). The 'value="...' part of the tag is an attribute of the tag, hence using `xml_attr()` or `xmlGetAttr` to retrieve it from the extracted node(s)
On Mon, Sep 21, 2015 at 3:41 PM, Glenn Schultz <glennmschu...@me.com> wrote: > Hi Bob, > > Thanks, can you help me undestand why it starts with //observation and how > you know that it is a node? > > Glenn > > On Sep 21, 2015, at 01:56 PM, boB Rudis <b...@rudis.net> wrote: > > This is how (one way) in both the xml2 package and XML package: > > library(xml2) > library(XML) > > txt <- '<?xml version="1.0" encoding="utf-8"?> > <observations realtime_start="2015-09-21" realtime_end="2015-09-21" > observation_start="2015-09-01" observation_end="2015-09-01" > units="lin" output_type="1" file_type="xml" > order_by="observation_date" sort_order="asc" count="1" offset="0" > limit="100000"> > <observation realtime_start="2015-09-21" realtime_end="2015-09-21" > date="2015-09-01" value="0.46"/> > </observations>' > > doc <- read_xml(txt) > xml_attr(xml_find_all(doc, "//observation"), "value") > > doc1 <- xmlParse(txt) > xpathSApply(doc1, "//observation", xmlGetAttr, "value") > > > > On Mon, Sep 21, 2015 at 2:01 PM, Glenn Schultz <glennmschu...@me.com> wrote: > > <?xml version="1.0" encoding="utf-8"?> > > <observations realtime_start="2015-09-21" realtime_end="2015-09-21" > > observation_start="2015-09-01" observation_end="2015-09-01" units="lin" > > output_type="1" file_type="xml" order_by="observation_date" sort_order="asc" > > count="1" offset="0" limit="100000"> > > <observation realtime_start="2015-09-21" realtime_end="2015-09-21" > > date="2015-09-01" value="0.46"/> > > </observations> ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
