How to parse sub path of an XML file using XML2 package - r

Question

I have the following xml page that looks like this which I need to parse using xml2
However, with this code, I cannot get the list under the subcellularLocation xpath :
library(xml2)
xmlfile <- "https://www.uniprot.org/uniprot/P09429.xml"
doc <- xmlfile %>%
xml2::read_xml()
xml_name(doc)
xml_children(doc)
x <- xml_find_all(doc, "//subcellularLocation")
xml_path(x)
# character(0)
What is the right way to do it?
Update
The desired output is a vector:
[1] "Nucleus"
[2] "Chromosome"
[3] "Cytoplasm"
[4] "Secreted"
[5] "Cell membrane"
[6] "Peripheral membrane protein"
[7] "Extracellular side"
[8] "Endosome"
[9] "Endoplasmic reticulum-Golgi intermediate compartment"

Answer 1

Use x <- xml_find_all(doc, "//d1:subcellularLocation")
Whenever you meet a troublesome problem, check the document is the first thing to do, use ?xml_find_all and you will see this (at the end of the page)
# Namespaces ---------------------------------------------------------------
# If the document uses namespaces, you'll need use xml_ns to form
# a unique mapping between full namespace url and a short prefix
x <- read_xml('
<root xmlns:f = "http://foo.com" xmlns:g = "http://bar.com">
<f:doc><g:baz /></f:doc>
<f:doc><g:baz /></f:doc>
</root>
')
xml_find_all(x, ".//f:doc")
xml_find_all(x, ".//f:doc", xml_ns(x))
So you then go to check xml_ns(doc) and find
d1 <-> http://uniprot.org/uniprot
xsi <-> http://www.w3.org/2001/XMLSchema-instance
Update
xml_find_all(doc, "//d1:subcellularLocation")
%>% xml_children()
%>% xml_text()
## [1] "Nucleus"
## [2] "Chromosome"
## [3] "Cytoplasm"
## [4] "Secreted"
## [5] "Cell membrane"
## [6] "Peripheral membrane protein"
## [7] "Extracellular side"
## [8] "Endosome"
## [9] "Endoplasmic reticulum-Golgi intermediate compartment"ent"

Answer 2

If you don't mind, you can use the rvest package:
library(rvest)
a=read_html(xmlfile)%>%
html_nodes("subcellularlocation")
a%>%html_children()%>%html_text()
[1] "Nucleus" "Chromosome"
[3] "Cytoplasm" "Secreted"
[5] "Cell membrane" "Peripheral membrane protein"
[7] "Extracellular side" "Endosome"
[9] "Endoplasmic reticulum-Golgi intermediate compartment"