Hi Rgonauts,
I am trying to parse some xml files of transport data using the TransExchange
format (in this case bus routing information) and obtain some data.frames for
onward processing for a GIS related task. Ideally I need them in .csv files.
Each file (an example is attached) contains up to 8 tables of information about
transport operators and routing information. I have uploaded an example that
contains all 8. In fact I have some hundreds of similar files that will need
processing. So when I've solved this I will need to be able to loop through a
bunch of them.
I'm new to handling xml data and to the xml package so I don't really know what
I'm doing, this is my first stab at using the xml package.
So far the workflow goes something like this.
#get the file
doc=xmlTreeParse("cen_18-23-D-y11-2.xml")
top=xmlRoot(doc)
#look at the names
top=xmlRoot(doc)
#pick one of them to use, in this case the forth one, 'routes', a table of
information about this particular bus route. using some code from another forum
post, I can get a data.frame with the info i need in it. OK I need to do some
reshaping but I can handle that later
fr4<-(top[[4]])
fr4
xmlSApply(fr4,function(x) xmlSApply(x,xmlValue))
df<-as.data.frame(xmlSApply(fr4,function(x) xmlSApply(x,xmlValue)))
df
#this works but when I try it with another table, the fifth one say, that
captures information about the parts of the journey between stops, it falls
over.
fr5<-(top[[5]])
fr5
xmlSApply(fr5,function(x) xmlSApply(x,xmlValue))
df<-as.data.frame(xmlSApply(fr5,function(x) xmlSApply(x,xmlValue)))
df
Now I guess there is an irregularity in the xml causing this. I gather from
other posts I should use Xpath functionality to interrogate this section of the
data. I've tried reverse engineering some of these commands I've seen in
solutions to irregular xml problems on other forums but not got to what I want.
I'm not really up on xml, but I am assuming it is something to do with the
<JourneySectionPattern id=****> part of the file is what is causing the
problem? This looks like there should be a field called JouneyPattern ID (only
I guess without the space) and then the ID code as the actual field contents.
So my question is, is there a way to parse this table correctly and output the
resulting df as a csv?
All help gratefully recieved. BTW the link to the searhable r-help archives
seems to be broken.
GavinR
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