Citations are a crucial piece of scholarly work. They hold metadata on each scholarly work, including what people were involved, what year the work was published, where it was published, and more. The links between citations facilitate insight into many questions about scholarly work.

Citations come in many different formats including BibTex, RIS, JATS, and many more. This is not to be confused with citation styles such as APA vs. MLA and so on.

Those that deal with or do research on citations often get citations in one format (e.g., BibTex), but they would like them in a different format (e.g., RIS). One recent tool that does a very nice job of this is bolognese from Martin Fenner of Datacite. bolognese is written in Ruby. I love the Ruby language, but it does not play nicely with R; thus it wasn’t an option to wrap or call bolognese from R.

handlr is a new R package modeled after bolognese.

The original motivation for starting handlr comes from this thread in the rorcid package, in which the citations retrieved from source A had mangled characters with accents, but source B gave un-mangled characters but in the wrong format. Thus the need for a citation format converter.

handlr converts citations from one format to another. It currently supports reading the following formats:

• citeproc
• ris
• bibtex
• codemeta

And the following writers are supported:

• citeproc
• ris
• bibtex
• schema.org
• rdfxml (requires suggested package jsonld)
• codemeta

handlr has not yet focused on performance, but we will do so in future versions.

Links:

• handlr source code: https://github.com/ropensci/handlr
• handlr on CRAN: https://cran.rstudio.com/web/packages/handlr/

Installation

Install the lastest from CRAN

install.packages("handlr")

Some binaries are not up yet on CRAN – you can also install from GitHub. There’s no compiled code though, so source install should work. I somehow forgot to export the print.handl() function in the CRAN version, so if you try this with the CRAN version you won’t get the compact output seen below.

remotes::install_github("ropensci/handlr")

Load handlr

library(handlr)

The R6 approach

There’s a single R6 interface to all readers and writers

grab an example file that comes with the package

z <- system.file("extdata/citeproc.json", package = "handlr")

initialize the object

x <- HandlrClient$new(x = z)
x
#> <handlr> 
#>   doi: 
#>   ext: json
#>   format (guessed): citeproc
#>   path: /Library/Frameworks/R.framework/Versions/3.5/Resources/library/handlr/extdata/citeproc.json
#>   string (abbrev.): none

read the file

x$read(format = "citeproc")
x
#> <handlr> 
#>   doi: 
#>   ext: json
#>   format (guessed): citeproc
#>   path: /Library/Frameworks/R.framework/Versions/3.5/Resources/library/handlr/extdata/citeproc.json
#>   string (abbrev.): none

inspect the parsed content

x$parsed
#> <handl> 
#>   from: citeproc
#>   many: FALSE
#>   count: 1
#>   first 10 
#>     id/doi: https://doi.org/10.5438/4k3m-nyvg

write out to bibtex. by default does not write to a file; you can also specify a file path.

cat(x$write("bibtex"), sep = "\n")
#> @article{https://doi.org/10.5438/4k3m-nyvg,
#>   doi = {10.5438/4k3m-nyvg},
#>   author = {Martin Fenner},
#>   title = {Eating your own Dog Food},
#>   journal = {DataCite Blog},
#>   pages = {},
#>   publisher = {DataCite},
#>   year = {2016},
#> }

Function approach

If you prefer not to use the above approach, you can use the various functions that start with he format (e.g., bibtex) followed by _reader or _writer.

Here, we play with the bibtex format.

Get a sample file and use bibtex_reader() to read it in.

z <- system.file('extdata/bibtex.bib', package = "handlr")
bibtex_reader(x = z)
#> <handl> 
#>   from: bibtex
#>   many: FALSE
#>   count: 1
#>   first 10 
#>     id/doi: https://doi.org/10.1142%2fs1363919602000495

What this returns is a handl object, just a list with attributes. The handl object is what we use as the internal representation that we convert citations to and from.

Each reader and writer supports handling many citations at once. For all formats, this means many citations in the same file.

z <- system.file('extdata/bib-many.bib', package = "handlr")
bibtex_reader(x = z)
#> <handl> 
#>   from: bibtex
#>   many: TRUE
#>   count: 2
#>   first 10 
#>     id/doi: https://doi.org/10.1093%2fbiosci%2fbiw022
#>     id/doi: https://doi.org/10.1890%2f15-1397.1

To do

• There’s still definitely some improvements that need to be made to various parts of citations in some of the formats. Do open an issue/let me know if you find anything off.
• Performance could be improved for sure
• Problems with very large files, e.g., ropensci/handlr#9
• Documentation, there is very little thus far

Get in touch

Get in touch if you have any handlr questions in the issue tracker or the rOpenSci discussion forum.