Interactive Overlays on the basis of Aggregated Journal-Journal Citations in the Journal Citation Reports 2012
The procedure for generating overlay maps on the basis of journals in 2012 can be considered as an update to the one for 2011 data (Leydesdorff, Rafols, & Chen, 2013). However, clustering is now based on the algorithm provided in VOSviewer as default. The number of journals included in 2012 is 10,936 (JCR 2012 for the Science Edition and Social Science Edition combined, October 2013). The map is based on the 10,546 journals in the largest component. See for more details: Leydesdorff, de Moya-Anegón, & de Nooy (in preparation). The purpose of this project is a comparison with a similar map using Scopus data; see at http://www.leydesdorff.net/scopus12 .
Figure 1 shows the base map 2012 on the basis of JCR-2012 data:
Figure 1: Citing patterns of 10,546 journals in JCR 2012 visualized as a base map; cosine > .2; colors correspond to 11 communities distinguished by VOSviewer.
This file can be web started at http://www.vosviewer.com/vosviewer.php?map=http://www.leydesdorff.net/journals12/jcr12.txt .
The overlays can be made on the basis of any retrieval from the (Social) Science Citation Index at the Web-of-Science. Three programs are made available online for generating these overlays. Two of them, “citing.exe” (at http://www.leydesdorff.net/journals12/citing.exe) and “crciting.exe” (at http://www.leydesdorff.net/journals12/crciting.exe) can process sets of documents downloaded from WoS in the so-called “tagged” format (that is, with labels like “AU ” for authors, “TI ” for titles, etc.). The input file has to be renamed “data.txt”. Citing.exe maps the journals in which the publications appeared and CrCiting.exe the journal abbreviations of the journals cited in these documents. Equivalent routines in the cited dimension are only available for 2011 at http://www.leydesdorff.net/journals11.
The third routine “analyze.exe” (at http://www.leydesdorff.net/journals12/analyze.exe) uses the results of the retrieval directly from of the option “Analyze Results” at WoS and does therefore not require downloading the set(s). This latter option is the most efficient procedure for making a journal map for this data. One maps the publishing journals.
Instruction for the construction of journal overlay maps 2012 (10,546 journals):
a. Generating journal maps of science without downloading the sets (that is, from the retrieval at WoS):
After entering one’s search results at WoS, one can click in the left column at the bottom on “Analyze Results”. In the Results Analysis that then opens as a next screen, one selects “Source Titles”; select “minimum records” (e.g., 1) and “Show” (e.g., 500). Thereafter select “All data rows”—different from the default option—and save the results to the file analyze.txt (the default). Analyze.exe reads this file, and generates an output file (citing.txt) for VOSViewer if the file “citing.dbf” is also present.
Note that analyze.txt is not overwritten in case of a next run, but a new file analyze(1).txt (etc.) is generated by WoS. Rename this file before further processing. Analyze.exe overwrites files from previous runs.
b. Using downloaded sets:
Two programs are made available online at http://www.leydesdorff.net/journals12/citing.exe and http://www.leydesdorff.net/journals12/crciting.exe, respectively, for processing any file containing downloaded data from WoS. These .exe files also require the presence of the table file http://www.leydesdorff.net/journals12/citing.dbf in the same folder on your hard disk. (Right-click on the link for saving if necessary!) In addition to the coordinate information for the maps, the full and abbreviated titles of the journals as provided by the JCRs are listed in these files. These titles are used as keys for the matching. (In the case of an unforeseen mismatch—for example, because of a title change—one is advised to adapt the title in the corresponding table file.)
When the programs and tables are brought into a single folder with the input file (data.txt or analyze.txt, respectively), an output file can be generated. This file is called “citing.txt” and can be used as input to VOSViewer and thus be visualized as overlays.
Figure 2 shows the overlay map 2012 of the journal publication portfolios from 2006 to 2010 of the Science and Technology Policy Research Unit SPRU at the University of Sussex (N = 148; Rao-Stirling diversity = 0.216; available at http://www.vosviewer.com/vosviewer.php?map=http://www.leydesdorff.net/journals12/spru.txt&label_size=1.35) . This file can be compared with the map based on 2011 data in Leydesdorff et al. (2013, p. 2579) available at http://www.vosviewer.com/vosviewer.php?map=http://www.leydesdorff.net/journals11/fig3a.txt&label_size=1.35). The Rao-Stirling diversity was virtually similar (0.218) in that case. As noted, the colouring in this latter figure was based on a different clustering algorithm (Blondel et al., 2008)
Interdisciplinarity and diversity
Both analyze.exe and citing.exe end with a message to the screen of the Rao-Stirling diversity. This value is also written to the file “rao.txt” in the same directory. The measure provides an index between 0 and 1 of the interdisciplinarity of the set under study in terms of aggregated journal-journal citations 2011 (see also Leydesdorff & Rafols, 2011).
Clustering and coloring
In the 2012 version we use the results of the clustering algorithm available in VOSviewer and no longer the community-finding algorithm of Blondel et al. (2008). However, the results of this alternate colouring are available in the file citing.dbf. Using Excel, for example, one can replace the values of the field “cluster” with these values under the field “blondel”. Be careful to save the file back as dBase file with the name “citing.dbf”. (If necessary use OpenOffice or SPSS when Excel fails to do this correctly.)
I am grateful to Thomson-Reuters for providing the underlying data.
Chen, C., & Leydesdorff, L. (in press). Patterns of Connections and Movements in Dual-Map Overlays: A New Method of Publication Portfolio Analysis Journal of the American Society for Information Science and Technology.
Leydesdorff, L., & Rafols, I. (2011). Indicators of the interdisciplinarity of journals: Diversity, centrality, and citations. Journal of Informetrics, 5(1), 87-100.
Leydesdorff, L., & Rafols, I. (2012). Interactive Overlays: A New Method for Generating Global Journal Maps from Web-of-Science Data. Journal of Informetrics, 6(3), 318-332.
Leydesdorff, L., de Moya Anegón, F., & de Nooy, W. (in preparation). Journal Maps and Interactive Overlays of Scopus and Web-of-Science 2012: The two aggregated journal-journal citation networks compared.
Waltman, L., van Eck, N. J., & Noyons, E. (2010). A unified approach to mapping and clustering of bibliometric networks. Journal of Informetrics, 4(4), 629-635.