  Using "Analyze Results" at the Web of Science, one can directly generate
overlays onto global journal maps of science. The maps are based on the 10,000+
journals contained in the Journal Citation Reports (JCR) of the Science and
Social Science Citation Indices (2011). The disciplinary diversity of the
retrieval is measured in terms of Rao-Stirling's "quadratic entropy." Since
this indicator of interdisciplinarity is normalized between zero and one, the
interdisciplinarity can be compared among document sets and across years, cited
or citing. The colors used for the overlays are based on Blondel et al.'s
(2008) community-finding algorithms operating on the relations journals
included in JCRs. The results can be exported from VOSViewer with different
options such as proportional labels, heat maps, or cluster density maps. The
maps can also be web-started and/or animated (e.g., using PowerPoint). The
"citing" dimension of the aggregated journal-journal citation matrix was found
to provide a more comprehensive description than the matrix based on the cited
archive. The relations between local and global maps and their different
functions in studying the sciences in terms of journal litteratures are further
discussed: local and global maps are based on different assumptions and can be
expected to serve different purposes for the explanation.
