Some text.
Some other.
No bold text
") para <- xml_find_all(x, ".//p") b <- xml_find_first(para, ".//b") mss <- b[[3]] test_that("xml_find returns nodes of class 'xml_missing' for missing nodes", { expect_equal(length(b), 3L) expect_equal(vapply(b, length, integer(1)), c(2L, 2L, 0L)) expect_is(mss, "xml_missing") }) test_that("xml_missing methods return properly for all S3 methods", { expect_equal(as.character(mss), NA_character_) expect_equal(as_list(mss), list()) expect_equal(nodeset_apply(mss), xml_nodeset()) expect_output(print(mss), "\\{xml_missing\\}\n Y2?QV'aCC6 )eYzJ\7= @x.*rlahx
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ϧF50 43f`LۓU7oE5 = |yHc_w73HR1JXP 5: 5H|gӥ N ܄D2lȬ]@CY Some text. Some other. No bold text Some text. Some other. No bold text Modifying existing XML can be done in xml2 by using the replacement functions of the accessors. They all have methods for both individual Text modification only happens on text nodes. If a given node has more than one text node only the first will be affected. If you want to modify additional text nodes you need to select them explicitly with Attributes and namespace definitions are modified one at a time with All of these functions have a The This allows code like the following to work without crashing R If you are not planning on referencing these nodes again this memory is wasted. Calling In particular We want to construct a document with the following namespace layout. (From http://stackoverflow.com/questions/32939229/creating-xml-in-r-with-namespaces/32941524#32941524). R is a free software environment for statistical computing and graphics. It compiles and runs on a wide variety of UNIX platforms, Windows and MacOS. To download R, please choose your preferred CRAN mirror. If you have questions about R like how to download and install the software, or what the license terms are, please read our answers to frequently asked questions before you send an email. R 3.2.0 (Full of Ingredients) prerelease versions will appear starting March 19. Final release is scheduled for 2015-04-16. R version 3.1.3 (Smooth Sidewalk) has been released on 2015-03-09. The R Journal Volume 6/2 is available. R version 3.1.2 (Pumpkin Helmet) has been released on 2014-10-31. useR! 2015, will take place at the University of Aalborg, Denmark, June 30 - July 3, 2015. useR! 2014, took place at the University of California, Los Angeles, USA June 30 - July 3, 2014.Node Modification
Jim Hester
2020-04-08
Modifying Existing XML
xml_node objects as well as xml_nodeset objects. If a vector of values is provided it is applied piecewise over the nodeset, otherwise the value is recycled.Text Modification
/text().x <- read_xml("<p>This is some <b>text</b>. This is more.</p>")
xml_text(x)
#> [1] "This is some text. This is more."
xml_text(x) <- "This is some other text."
xml_text(x)
#> [1] "This is some other text.text. This is more."
# You can avoid this by explicitly selecting the text node.
x <- read_xml("<p>This is some text. This is <b>bold!</b></p>")
text_only <- xml_find_all(x, "//text()")
xml_text(text_only) <- c("This is some other text. ", "Still bold!")
xml_text(x)
#> [1] "This is some other text. Still bold!"
xml_structure(x)
#> <p>
#> {text}
#> <b>
#> {text}Attribute and Namespace Definition Modification
xml_attr() or all at once with xml_attrs(). In both cases using NULL as the value will remove the attribute completely.x <- read_xml("<a href='invalid!'>xml2</a>")
xml_attr(x, "href")
#> [1] "invalid!"
xml_attr(x, "href") <- "https://github.com/r-lib/xml2"
xml_attr(x, "href")
#> [1] "https://github.com/r-lib/xml2"
xml_attrs(x) <- c(id = "xml2", href = "https://github.com/r-lib/xml2")
xml_attrs(x)
#> href id
#> "https://github.com/r-lib/xml2" "xml2"
x
#> {xml_document}
#> <a href="https://github.com/r-lib/xml2" id="xml2">
xml_attrs(x) <- NULL
x
#> {xml_document}
#> <a>
# Namespaces are added with as a xmlns or xmlns:prefix attribute
xml_attr(x, "xmlns") <- "http://foo"
x
#> {xml_document}
#> <a xmlns="http://foo">
xml_attr(x, "xmlns:bar") <- "http://bar"
x
#> {xml_document}
#> <a xmlns="http://foo" xmlns:bar="http://bar">Node modification
.copy argument. If this is set to FALSE they will remove the new node from its location before inserting it into the new location. Otherwise they make a copy of the node before insertion.Replacing existing nodes
x <- read_xml("<parent><child>1</child><child>2<child>3</child></child></parent>")
children <- xml_children(x)
t1 <- children[[1]]
t2 <- children[[2]]
t3 <- xml_children(children[[2]])[[1]]
xml_replace(t1, t3)
#> {xml_node}
#> <child>
x
#> {xml_document}
#> <parent>
#> [1] <child>3</child>
#> [2] <child>2<child>3</child></child>Add a sibling
x <- read_xml("<parent><child>1</child><child>2<child>3</child></child></parent>")
children <- xml_children(x)
t1 <- children[[1]]
t2 <- children[[2]]
t3 <- xml_children(children[[2]])[[1]]
xml_add_sibling(t1, t3)
x
#> {xml_document}
#> <parent>
#> [1] <child>1</child>
#> [2] <child>3</child>
#> [3] <child>2<child>3</child></child>
xml_add_sibling(t3, t1, where = "before")
x
#> {xml_document}
#> <parent>
#> [1] <child>1</child>
#> [2] <child>3</child>
#> [3] <child>2<child>3</child><child>1</child></child>Add a child
x <- read_xml("<parent><child>1</child><child>2<child>3</child></child></parent>")
children <- xml_children(x)
t1 <- children[[1]]
t2 <- children[[2]]
t3 <- xml_children(children[[2]])[[1]]
xml_add_child(t1, t3)
x
#> {xml_document}
#> <parent>
#> [1] <child>1<child>3</child></child>
#> [2] <child>2<child>3</child></child>
xml_add_child(t1, read_xml("<test/>"))
x
#> {xml_document}
#> <parent>
#> [1] <child>1<child>3</child><test/></child>
#> [2] <child>2<child>3</child></child>Removing nodes
xml_remove() can be used to remove a node (and its children) from a tree. The default behavior is to unlink the node from the tree, but does not free the memory for the node, so R objects pointing to the node are still valid.x <- read_xml("<foo><bar><baz/></bar></foo>")
x1 <- x %>% xml_children() %>% .[[1]]
x2 <- x1 %>% xml_children() %>% .[[1]]
xml_remove(x1)
rm(x1)
gc()
#> used (Mb) gc trigger (Mb) limit (Mb) max used (Mb)
#> Ncells 572101 30.6 1275621 68.2 NA 1272531 68.0
#> Vcells 1100538 8.4 8388608 64.0 32768 2035739 15.6
x2
#> {xml_node}
#> <baz>xml_remove(free = TRUE) will remove the nodes and free the memory used to store them. Note In this case any node which previously pointed to the node or its children will instead be pointing to free memory and may cause R to crash. xml2 can’t figure this out for you, so it’s your responsibility to remove any objects which are no longer valid.xml_find_*() results are easy to overlook, for examplex <- read_xml("<a><b /><b><b /></b></a>")
bees <- xml_find_all(x, "//b")
xml_remove(xml_child(x), free = TRUE)
# bees[[1]] is no longer valid!!!
rm(bees)
gc()
#> used (Mb) gc trigger (Mb) limit (Mb) max used (Mb)
#> Ncells 572148 30.6 1275621 68.2 NA 1272531 68.0
#> Vcells 1100589 8.4 8388608 64.0 32768 2035739 15.6Namespaces
<?xml version = "1.0" encoding="UTF-8"?>
<sld xmlns="http://www.o.net/sld"
xmlns:ogc="http://www.o.net/ogc"
xmlns:se="http://www.o.net/se"
version="1.1.0" >
<layer>
<se:Name>My Layer</se:Name>
</layer>
</sld>d <- xml_new_root("sld",
xmlns = "http://www.o.net/sld",
"xmlns:ogc" = "http://www.o.net/ogc",
"xmlns:se" = "http://www.o.net/se",
version = "1.1.0") %>%
xml_add_child("layer") %>%
xml_add_child("se:Name", "My Layer") %>%
xml_root()
d
#> {xml_document}
#> <sld version="1.1.0" xmlns="http://www.o.net/sld" xmlns:ogc="http://www.o.net/ogc" xmlns:se="http://www.o.net/se">
#> [1] <layer>\n <se:Name>My Layer</se:Name>\n</layer>
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