R help - Dec 2021 - Using R to convert RDF/XML to

Hello R community,

I am a novice R enthusiast trying to use R to convert an RDFdump file [1] from
Semantic Mediawiki [2] into something that can be natively imported by GePhi [3]
for graph visualization. The SMW RDFdump file is formatted as RDF/XML and I have
found the R package "rdflib" [4] and am able to read the RDF/XML file
into R as an "rdf" object, but it is not clear to me how to save the
"rdf_serialize" function output to a new file.

What I have so far is: 
library(rdflib)
NewRDF <- tempfile( "TempFile", fileext = ".nq" )
MyRDF <- rdf_parse( "MyRDFdumpFile.txt" )
rdf_serialize( MyRDF, NewRDF, format = "nquads"  )
write_nquads( MyRDF, NewRDF ) 

..but this results in the error: "Error: object of type 'closure'
is not subsettable"

I will keep struggling with this to learn what I need to learn, but any advice
to help make quick work of this would be much appreciated.

Thank you in advance.
/Rich

[1] https://www.semantic-mediawiki.org/wiki/Help:Maintenance_script_dumpRDF.php
[2]
https://www.semantic-mediawiki.org/wiki/Help:Introduction_to_Semantic_MediaWiki
[3] https://gephi.org/
[4] https://cran.r-project.org/web/packages/rdflib/rdflib.pdf

- Richard Evans, NASA GRC - Armstrong Test Facility
  mailto://richard.k.evans at nasa.gov 
? http://www.linkedin.com/in/rkevans

This is the sort of thing that you should first ask the package maintainer
about; there is an error in the rdf method for write_nquads:
> rdflib:::write_nquads.rdf
function (x, file, ...)
{
    rdf_serialize(rdf, file, "nquads", ...)
}

I suspect that the first argument to rdf_serialize should be 'x', not
'rdf'.

Another error in the package is that this function isn't tested.

-Bill


On Fri, Dec 31, 2021 at 6:19 AM Evans, Richard K. (GRC-H000) via R-help <
r-help at r-project.org> wrote:
> Hello R community,
>
> I am a novice R enthusiast trying to use R to convert an RDFdump file [1]
> from Semantic Mediawiki [2] into something that can be natively imported by
> GePhi [3] for graph visualization. The SMW RDFdump file is formatted as
> RDF/XML and I have found the R package "rdflib" [4] and am able
to read the
> RDF/XML file into R as an "rdf" object, but it is not clear to me
how to
> save the "rdf_serialize" function output to a new file.
>
> What I have so far is:
> library(rdflib)
> NewRDF <- tempfile( "TempFile", fileext = ".nq" )
> MyRDF <- rdf_parse( "MyRDFdumpFile.txt" )
> rdf_serialize( MyRDF, NewRDF, format = "nquads"  )
> write_nquads( MyRDF, NewRDF )
>
> ..but this results in the error: "Error: object of type
'closure' is not
> subsettable"
>
> I will keep struggling with this to learn what I need to learn, but any
> advice to help make quick work of this would be much appreciated.
>
> Thank you in advance.
> /Rich
>
> [1]
> https://www.semantic-mediawiki.org/wiki/Help:Maintenance_script_dumpRDF.php
> [2]
>
https://www.semantic-mediawiki.org/wiki/Help:Introduction_to_Semantic_MediaWiki
> [3] https://gephi.org/
> [4] https://cran.r-project.org/web/packages/rdflib/rdflib.pdf
>
> - Richard Evans, NASA GRC - Armstrong Test Facility
>   mailto://richard.k.evans at nasa.gov
>   http://www.linkedin.com/in/rkevans
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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