xml2 (version 1.0.0)

xml_attr: Retrieve an attribute.

Description

xml_attrs() retrieves all attributes values as a named character vector, xml_attrs() <- sets all attribute values. xml_attr() retrieves the value of single attribute and xml_attr() <- modifies its value. If the attribute doesn't exist, it will return default, which defaults to NA. xml_has_attr() tests if an attribute is present.

Usage

xml_attr(x, attr, ns = character(), default = NA_character_)
xml_has_attr(x, attr, ns = character())
xml_attrs(x, ns = character())
xml_attr(x, attr, ns = character()) <- value
xml_attrs(x, ns = character()) <- value

Arguments

x

A document, node, or node set.

attr

Name of attribute to extract.

ns

Optionally, a named vector giving prefix-url pairs, as produced by xml_ns. If provided, all names will be explicitly qualified with the ns prefix, i.e. if the element bar is defined in namespace foo, it will be called foo:bar. (And similarly for atttributes). Default namespaces must be given an explicit name.

default

Default value to use when attribute is not present.

value

character vector of new value.

Value

xml_attr() returns a character vector. NA is used to represent of attributes that aren't defined.xml_has_attr() returns a logical vector.xml_attrs() returns a named character vector if x x is single node, or a list of character vectors if given a nodeset

Examples

x <- read_xml("<root id='1'><child id ='a' /><child id='b' d='b'/></root>")
xml_attr(x, "id")
xml_attr(x, "apple")
xml_attrs(x)

kids <- xml_children(x)
kids
xml_attr(kids, "id")
xml_has_attr(kids, "id")
xml_attrs(kids)

# Missing attributes give missing values
xml_attr(xml_children(x), "d")
xml_has_attr(xml_children(x), "d")

# If the document has a namespace, use the ns argument and
# qualified attribute names
x <- read_xml('
 <root xmlns:b="http://bar.com" xmlns:f="http://foo.com">
   <doc b:id="b" f:id="f" id="" />
 </root>
')
doc <- xml_children(x)[[1]]
ns <- xml_ns(x)

xml_attrs(doc)
xml_attrs(doc, ns)

# If you don't supply a ns spec, you get the first matching attribute
xml_attr(doc, "id")
xml_attr(doc, "b:id", ns)
xml_attr(doc, "id", ns)