Apr 21 2015
2 min

Parse and process XML (and HTML) with xml2

I’m pleased to announced that the first version of xml2 is now available on CRAN. Xml2 is a wrapper around the comprehensive libxml2 C library that makes it easier to work with XML and HTML in R:

• Read XML and HTML with read_xml() and read_html().

• Navigate the tree with xml_children(), xml_siblings() and xml_parent(). Alternatively, use xpath to jump directly to the nodes you’re interested in with xml_find_one() and xml_find_all(). Get the full path to a node with xml_path().

• Extract various components of a node with xml_text(), xml_attrs(), xml_attr(), and xml_name().

• Convert to list with as_list().

• Where appropriate, functions support namespaces with a global url -> prefix lookup table. See xml_ns() for more details.

• Convert relative urls to absolute with url_absolute(), and transform in the opposite direction with url_relative(). Escape and unescape special characters with url_escape() and url_unescape().

• Support for modifying and creating xml documents in planned in a future version.

This package owes a debt of gratitude to Duncan Temple Lang who’s XML package has made it possible to use XML with R for almost 15 years!

## Usage

You can install it by running:

install.packages("xml2")


(If you’re on a mac, you might need to wait a couple of days - CRAN is busy rebuilding all the packages for R 3.2.0 so it’s running a bit behind.)

Here’s a small example working with an inline XML document:

library(xml2)
<bar>text <baz id = 'a' /></bar>
<bar>2</bar>
<baz id = 'b' />
</foo>")

xml_name(x)
#> [1] "foo"
xml_children(x)
#> {xml_nodeset (3)}
#> [1] <bar>text <baz id="a"/></bar>
#> [2] <bar>2</bar>
#> [3] <baz id="b"/>

# Find all baz nodes anywhere in the document
baz <- xml_find_all(x, ".//baz")
baz
#> {xml_nodeset (2)}
#> [1] <baz id="a"/>
#> [2] <baz id="b"/>
xml_path(baz)
#> [1] "/foo/bar[1]/baz" "/foo/baz"
xml_attr(baz, "id")
#> [1] "a" "b"


## Development

Xml2 is still under active development. If notice any problems (including crashes), please try the development version, and if that doesn’t work, file an issue.

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