[R] Relational Databases or XML?

[Doran, Harold]

Well, I guess it is possible with XML package on CRAN. But, it seems
there is no windows binary (yet)

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Doran, Harold
> Sent: Thursday, April 10, 2008 4:29 PM
> To: Keith Alan Chamberlain; r-help at r-project.org
> Subject: Re: [R] Relational Databases or XML?
> 
> I'm not sure it is possible to parse an XML file in R 
> directly. Well, I guess it's *possible*, but may not be the 
> best way to do it. ElementTree in Python is an easy-to-use 
> parser that you might use to first parse your XML file (or 
> others hierarchically structured data), organize it anyway 
> you want, and then bring those data into R for subsequent analysis.
> 
> In fact, I have recently done just this. I have another 
> statistical program that outputs data as an XML file. So, I 
> wrote a python program that parses that XML file, pulls out 
> the data of interest into a text file, and then I bring those 
> data into R for analysis.
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org
> > [mailto:r-help-bounces at r-project.org] On Behalf Of Keith Alan 
> > Chamberlain
> > Sent: Thursday, April 10, 2008 4:14 PM
> > To: r-help at r-project.org
> > Subject: [R] Relational Databases or XML?
> > 
> > Dear R-Help,
> > 
> > I am working on a paper in an R course for large file support in R 
> > using scan(), relational databases, and XML. I have never 
> used SQL or 
> > heirarchical document formats such as XML (except where it occurs 
> > without user interaction), and knowledge in RDBs and XML is 
> lacking in 
> > my program. I have tried finding a working example for the 
> > novices-novice on the topic, read many postings, the r-data 
> I/O manual 
> > several times, and descriptions of packages RODBC, DBI, XML, among 
> > others. I understand that RDBs are (assumed at least) used widely 
> > among the R community. I have not been able to put all of 
> the pieces 
> > together, but assuming that RDB use is actually quite 
> widespread, it 
> > should be quite easy to fill me in and/or correct my understanding 
> > where necessary.
> > 
> > For a cross-platform solution (PC/OSX at least, or in part) my 
> > questions/problems are about what preliminary steps are 
> needed to get 
> > an SQL or XML query "to work" in R to begin with, what the 
> appropriate 
> > data-file formats are, and how to convert to them if 
> starting out with 
> > data in, say, a delimited ASCII text file. Very basic 
> examples should 
> > suffice, say, a table with 20 random observations, a 
> grouping variable 
> > with 2 levels, and a factor with 2 levels.
> > 
> > ## untested code
> > set.seed(1024)
> > write.table("junk.txt",
> > data.frame(Subj=c(rep(1,10),rep(2,10)),block=rep(c(rep(-1,5),r
> > ep(1,5)),2), obs=rnorm(20,0,1)))
> > 
> > Specifically,
> > 
> > 1- what are the minimum required non R components that are 
> needed to 
> > support SQL or XML functionality, which may or may not need to be 
> > installed?
> > 
> > 2- what R packages need to be installed, at a minimum (also as a 
> > cross-PC/Mac solution if possible or at least as much as
> > possible)
> > 
> > 3- I keep seeing reference to connections of a given name "if 
> > previously setup". What kind of setup is needed outside of 
> R, if any?
> > 
> > 4- what steps are needed in R to then connect to a file and 
> import a 
> > subset based on a query?
> > 
> > 5- Do I then use standard R routines (e.g. write()) to 
> export as a DB, 
> > or an RDB/XML specific function?
> > 
> > Sincerely,
> > KeithC. [U.S]
> > 
> > 1/k^c
> > 
> > ______________________________________________
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> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> > 
> 
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