格式化saveXML输出以保留R中的树结构

Question

I have a very long xml file that I am generating in R, and when I print the final xml to the console, it keeps the visual tree structure that makes the output easy for a human to read. When I write it to a file using saveXML though, it prints out one HUGE single line. Does anyone know how to get the saveXML function to print this and maintain the multi-line tree structure? I have looked everywhere and cannot find a solution.

A small toy example (with code taken from https://stat.ethz.ch/pipermail/r-help/2008-September/175364.html ) :

data <- read.csv(textConnection('"date","UYG.Open","UYG.High","UYG.Low","UYG.Close","UYG.Volume","UYG.Adjusted"
                      "2007-02-01",71.32,71.34,71.32,71.34,200,69.23
                      "2007-02-02",72.2,72.2,72.2,72.2,200,70.06
                      "2007-02-05",71.76,71.76,71.76,71.76,5100,69.63
                      "2007-02-06",72.85,72.85,72.85,72.85,3800,70.69
                      "2007-02-07",72.85,72.85,72.85,72.85,0,70.69'),
       as.is=TRUE)

 library(XML)

xml <- xmlTree()
xml$addTag("document", close=FALSE)
for (i in 1:nrow(data)) {
  xml$addTag("row", close=FALSE)
  for (j in names(data)) {
xml$addTag(j, data[i, j])
  }
   xml$closeTag()
}
    xml$closeTag()

# view the result
cat(saveXML(xml))

saveXML(xml, file="~/Desktop/xml_format_test.xml", compression = 0, indent=TRUE, prefix = '<?xml version="1.0"?>\n', doctype = NULL)

When I run the ' cat(saveXML(xml)) command, I get the following structure:

<?xml version="1.0"?>

<document>
  <row>
    <date>                          2007-02-01</date>
    <UYG.Open>71.32</UYG.Open>
    <UYG.High>71.34</UYG.High>
    <UYG.Low>71.32</UYG.Low>
    <UYG.Close>71.34</UYG.Close>
    <UYG.Volume>200</UYG.Volume>
    <UYG.Adjusted>69.23</UYG.Adjusted>
  </row>
  <row>
    <date>                          2007-02-02</date>
    <UYG.Open>72.2</UYG.Open>
    <UYG.High>72.2</UYG.High>
    <UYG.Low>72.2</UYG.Low>
    <UYG.Close>72.2</UYG.Close>
    <UYG.Volume>200</UYG.Volume>
    <UYG.Adjusted>70.06</UYG.Adjusted>
  </row>
  <row>
    <date>                          2007-02-05</date>
    <UYG.Open>71.76</UYG.Open>
    <UYG.High>71.76</UYG.High>
    <UYG.Low>71.76</UYG.Low>
    <UYG.Close>71.76</UYG.Close>
    <UYG.Volume>5100</UYG.Volume>
    <UYG.Adjusted>69.63</UYG.Adjusted>
  </row>
  <row>
    <date>                          2007-02-06</date>
    <UYG.Open>72.85</UYG.Open>
    <UYG.High>72.85</UYG.High>
    <UYG.Low>72.85</UYG.Low>
    <UYG.Close>72.85</UYG.Close>
    <UYG.Volume>3800</UYG.Volume>
    <UYG.Adjusted>70.69</UYG.Adjusted>
  </row>
  <row>
    <date>                          2007-02-07</date>
    <UYG.Open>72.85</UYG.Open>
    <UYG.High>72.85</UYG.High>
    <UYG.Low>72.85</UYG.Low>
    <UYG.Close>72.85</UYG.Close>
    <UYG.Volume>0</UYG.Volume>
    <UYG.Adjusted>70.69</UYG.Adjusted>
  </row>
</document>

But when I print this using saveXML(xml, file="~/Desktop/xml_format_test.xml", compression = 0, indent=TRUE, prefix = '<?xml version="1.0"?>\\n', doctype = NULL) , I get the following structure:

<?xml version="1.0"?>
 <document>   <row>     <date>                          2007-02-01</date>     <UYG.Open>71.32</UYG.Open>     <UYG.High>71.34</UYG.High>     <UYG.Low>71.32</UYG.Low>     <UYG.Close>71.34</UYG.Close>     <UYG.Volume>200</UYG.Volume>     <UYG.Adjusted>69.23</UYG.Adjusted>   </row>   <row>     <date>                          2007-02-02</date>     <UYG.Open>72.2</UYG.Open>     <UYG.High>72.2</UYG.High>     <UYG.Low>72.2</UYG.Low>     <UYG.Close>72.2</UYG.Close>     <UYG.Volume>200</UYG.Volume>     <UYG.Adjusted>70.06</UYG.Adjusted>   </row>   <row>     <date>                          2007-02-05</date>     <UYG.Open>71.76</UYG.Open>     <UYG.High>71.76</UYG.High>     <UYG.Low>71.76</UYG.Low>     <UYG.Close>71.76</UYG.Close>     <UYG.Volume>5100</UYG.Volume>     <UYG.Adjusted>69.63</UYG.Adjusted>   </row>   <row>     <date>                          2007-02-06</date>     <UYG.Open>72.85</UYG.Open>     <UYG.High>72.85</UYG.High>     <UYG.Low>72.85</UYG.Low>     <UYG.Close>72.85</UYG.Close>     <UYG.Volume>3800</UYG.Volume>     <UYG.Adjusted>70.69</UYG.Adjusted>   </row>   <row>     <date>                          2007-02-07</date>     <UYG.Open>72.85</UYG.Open>     <UYG.High>72.85</UYG.High>     <UYG.Low>72.85</UYG.Low>     <UYG.Close>72.85</UYG.Close>     <UYG.Volume>0</UYG.Volume>     <UYG.Adjusted>70.69</UYG.Adjusted>   </row> </document>

I really need the output format in the multi-line tree format for ease of visualization and to help new users understand the output. Any help is greatly appreciated as I have tried to find the solution for a few hours and cannot.

Answer 1

You could just use the file argument to cat() :

cat(saveXML(xml), file="~/Desktop/xml_format_test.xml")

Looks like this bug was spotted some years ago but still hasn't been fixed.