stefan.d...@gmail.com wrote:
Hello,
I am trying to convert a simple data.frame (it will always be a few
equally long variables) into the XML format (which I don't understand
too well but need as input for another program) and reverse the
operation (from XML back into data.frame).
I found some code which does the first and it works good enough for me
(see below). Is there an easy way to reverse the operation?
> My XML
files are nothing fancy (no child nodes or anything, at least as far
as I can see.
Just for the record, there are child nodes.
You have a top-level node <populationsize>
This has several children <size>. And each of these has
<age>, <sex> and <number> as children.
You don't sub-nodes of these so the hierarchy is relatively flat
and does correspond to a data frame with each <size> node
as an observation and <age>, <sex> and <number> as variables/columns.
I wrote some relatively general functions, but hastily written functions
to read this sort of data. You can find them attached or at
http://www.omegahat.org/RSXML/xmlToDataFrame.xml
You can use these as
xmlToDataFrame("size.xml")
It handles homogeneous and non-homogeneous nodes
(i.e. with the same number and names of sub-nodes or not)
and also allows one to specify colClasses somewhat similar
to that in read.table() ( but not completely implemented yet).
These functions will most likely be in the next release of the XML
package.
Let me know if they don't work for your data.
D.
### data.frame
data<- as.data.frame(cbind(c( 0 , 1 ),c( 500 , 300),c(200, 400)))
names(data)<-c("age","0","1")
### converts data.frame into XML
xml <- xmlTree()
xml$addTag("populationsize", close=FALSE)
for (i in 1:nrow(data)) {
xml$addTag("size", close=FALSE)
for (j in names(data)) {
xml$addTag(j, data[i, j])
}
xml$closeTag()
}
xml$closeTag()
# view the result
cat(saveXML(xml))
I put below also an example of how my data looks like.
Thanks for any advice!
Best and have a great day,
Stefan
APPENDIX
XML-file
------------------
<populationsize>
<size>
<age>0</age>
<sex>0</sex>
<number>500</number>
</size>
<size>
<age>0</age>
<sex>1</sex>
<number>300</number>
</size>
<size>
<age>1</age>
<sex>0</sex>
<number>200</number>
</size>
<size>
<age>1</age>
<sex>1</sex>
<number>400</number>
</size>
</populationsize>
---------
DATAFRAME
age 0 1
0 500 300
1 200 400
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and provide commented, minimal, self-contained, reproducible code.
