  Under the data-driven research paradigm, research software has come to play
crucial roles in nearly every stage of scientific inquiry. Scholars are
advocating for the formal citation of software in academic publications,
treating it on par with traditional research outputs. However, software is
hardly consistently cited: one software entity can be cited as different
objects, and the citations can change over time. These issues, however, are
largely overlooked in existing empirical research on software citation. To fill
the above gaps, the present study compares and analyzes a longitudinal dataset
of citation formats of all R packages collected in 2021 and 2022, in order to
understand the citation formats of R-language packages, important members in
the open-source software family, and how the citations evolve over time. In
particular, we investigate the different document types underlying the
citations and what metadata elements in the citation formats changed over time.
Furthermore, we offer an in-depth analysis of the disciplinarity of journal
articles cited as software (software papers). By undertaking this research, we
aim to contribute to a better understanding of the complexities associated with
software citation, shedding light on future software citation policies and
infrastructure.
