Today we are pleased to release version 1.1.1 of xml2. xml2 makes it easy to read, create, and modify XML with R. You can install it with:

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install.packages("xml2")

As well as fixing many bugs, this release:

  • Makes it easier to create an modify XML

  • Improves roundtrip support between XML and lists

  • Adds support for XML validation and XSLT transformations.

You can see a full list of changes in the release notes . This is the first release maintained by Jim Hester .

Creating and modifying XML#

xml2 has been overhauled with a set of methods to make generating and modfying XML easier:

  • xml_new_root() can be used to create a new document and root node simultaneously.
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xml_new_root("x") %>%
  xml_add_child("y") %>%
  xml_root()
#> {xml_document}
#> <x>
#> [1] <y/>
  • New xml_set_text(), xml_set_name(), xml_set_attr(), and xml_set_attrs() make it easy to modify nodes within a pipeline.
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x <- read_xml("<a>
    <b />
    <c><b/></c>
  </a>")
x
#> {xml_document}
#> <a>
#> [1] <b/>
#> [2] <c>\n  <b/>\n</c>

x %>%
  xml_find_all(".//b") %>%
  xml_set_name("banana") %>%
  xml_set_attr("oldname", "b")
x
#> {xml_document}
#> <a>
#> [1] <banana oldname="b"/>
#> [2] <c>\n  <banana oldname="b"/>\n</c>

  • New xml_add_parent() makes it easy to insert a node as the parent of an existing node.

  • You can create more esoteric node types with xml_comment() (comments), xml_cdata() (CDATA nodes), and xml_dtd() (DTDs).

Coercion to and from R Lists#

xml2 1.1.1 improves support for converting to and from R lists, thanks in part to work by Peter Foley and Jenny Bryan . In particular xml2 now supports preserving the root node name as well as saving all xml2 attributes as R attributes. These changes allows you to convert most XML documents to and from R lists with as_list() and as_xml_document() without loss of data.

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x <- read_xml("<fruits><apple color = 'red' /></fruits>")
x
#> {xml_document}
#> <fruits>
#> [1] <apple color="red"/>
as_list(x)
#> $apple
#> list()
#> attr(,"color")
#> [1] "red"
as_xml_document(as_list(x))
#> {xml_document}
#> <apple color="red">

XML validation and xslt#

xml2 1.1.1 also adds support for XML validation, thanks to Jeroen Ooms . Simply read the document and schema files and call xml_validate().

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doc <- read_xml(system.file("extdata/order-doc.xml", package = "xml2"))
schema <- read_xml(system.file("extdata/order-schema.xml", package = "xml2"))
xml_validate(doc, schema)
#> [1] TRUE
#> attr(,"errors")
#> character(0)

Jeroen also released the first xml2 extension package in conjunction with xml2 1.1.1, xslt . xslt allows one to apply XSLT (Extensible Stylesheet Language Transformations) to XML documents, which are great for transforming XML data into other formats such as HTML.