R help - Sep 2015 - extracting a value from XML

Hi All,

I have been trying to extract a value from XML. ?I have been at it for several
days off and on and I can't seem to get my head around the problem. ? I
basically understand the examples in R help but I cannot replicate success with
the below?

I tried to use xmlValue(doc, "//[[value]]") but no success. ?All I
need is the 0.46 value. ?Any suggestions to help me along are greatly
appreciated.

Glenn

<?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>
?

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 <glennmschultz at 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>