add a sibling to a node of xml in R

Question

how to add siblings to a1 and a2 node in R?

input : <a><a1>123</a1> <a2>222</a2> </a>

target <a><a1>123</a1> <a2>222</a2> <a3>222</a3> </a>

library(xml2)
x <- read_xml("<a><a1>123</a1> <a2>222</a2>  </a>"); 
xml_add_sibling(xml_child(x), "<a3>string</a3>"); 
x

Currently, it outpus: <a><a1>123</a1> <<a3>string</a3>/> <a2>222</a2> </a>.

why there are another < and />? Thank you.

Answer 1

You haven't used the function parameters correctly. The second argument in xml_add_sibling is .value, and should be the tag name. Instead of giving the tag the tagname a3, you are giving it the tagname <a3>string</a3>, which is why your extra angle brackets have appeared.

Simply pass the tagname a3 to the .value argument and enter the contents of the tag in a subsequent unnamed argument as advised in the docs:

.value       node to insert.

...            If named attributes or namespaces to set on the node, if unnamed text to assign to the node.

library(xml2)

x <- read_xml("<a><a1>123</a1> <a2>222</a2>  </a>")
xml_add_sibling(xml_child(x), .value = "a3", 'string')
x
#> {xml_document}
#> <a>
#> [1] <a1>123</a1>
#> [2] <a3>string</a3>
#> [3] <a2>222</a2>