Просто используйте пакет XML .Например:
library(XML)
# from the package documentation:
b = newXMLNode("bob")
saveXML(b)
f = tempfile()
saveXML(b, f)
doc = xmlInternalTreeParse(f)
saveXML(doc)
con <- xmlOutputDOM()
con$addTag("author", "Duncan Temple Lang")
con$addTag("address", close=FALSE)
con$addTag("office", "2C-259")
con$addTag("street", "Mountain Avenue.")
con$addTag("phone", close=FALSE)
con$addTag("area", "908", attrs=c(state="NJ"))
con$addTag("number", "582-3217")
con$closeTag() # phone
con$closeTag() # address
saveXML(con$value(), file="out.xml")