Readers who wish to examine or interrogate the maps in greater detail can do so using the guidance set out below. Please note: VOSviewer requires that Java be installed on your computer (browser integration also varies).
1. Follow the relevant link to the map that you wish to examine:
2. The link (vosviewer.jnlp) will cause VOSviewer to start on your computer and this may be preceded by a request to allow a Java applet to open or run (Figure d) and then another for the program VOSviewer to 'run' or to 'open' (Figure e). To both of these requests, you must give your consent.
3. The program VOSviewer will then start, with the clustered and coloured nodes from the map you have chosen visible in the main panel (Figure f).
4. VOSviewer provides five perspectives on the map (Figure g) that allow users to navigate their way around maps and to alter the nature of the visualisation. In addition to the main panel, users can adjust the background colour, the relative and absolute size of nodes through the 'options' panel; they can search for individual nodes using the 'items' tab in the 'action' panel, and when the mouse is positioned over a particular node in the main panel, details on citations or links to or from the node are visible in the 'information panel' below.
5. For example: a black background colour can be given to the map by checking the relevant checkbox here (Figure h);
6. Or the citations information about a specific node (in this case the journal Nature) can be found by hovering the mouse above the relevant node in the 'main panel' (Figure i);
7. Or the nodes within a particular cluster can be examined by following the 'items' tab (Figure j).
For the present study, two maps of archaeological research domain are presented for archaeological research published over the last decade. These are:
1. a network map of co-cited sources (Figure 2)
2. a network map of co-cited authors (Figure 4)
In addition to these maps, I have also extracted the major terms that are used and include:
3. a network map of terms (Figure 6)
The first two network maps are based on co-citation and, therefore, identify the intellectual base/research core of sources and authors employed in archaeological research. The network of terms identifies the basic vocabulary of archaeology and its structure: in some senses this is also a map of the basic conceptual knowledge of archaeology as a discipline. Since these maps have been created through citations (or writing in the case of terms) by archaeological researchers, to a large degree clusters within these maps reflect the manner in which discipline practitioners see the associations and disassociation between aspects of the discipline as a whole. Further publications are in process that will examine in more detail the networks within particular areas of archaeological research (Sinclair in prep. a; in prep. b; in prep. c; in prep. d).
For each of the three network maps presented here (Figure 2, Figure 4 and Figure 6), there is a table with the clusters and their major/typical contents listed, a small-scale network map with some of the major clusters labelled and a larger scalable image that will allow readers to examine the maps in more detail. Finally, readers can also examine a live version of each of these maps using an online facility available for VOSviewer by clicking on the relevant hyperlink. The online maps avoid the issue of balancing the legibility of naming information for each node presented directly on the scalable images with the presentation and possible illegibility of presenting all the node names. This will make it possible for readers to explore any network map and to search each map in VOSviewer for specific potential sources, authors or terms and to explore their links to other nodes in the same map. For readers who wish to examine these maps further, a brief description of the process is outlined here. (See Box 5)
Before looking at any map in detail readers need to know that the process of clustering and mapping used by VOSviewer does not always generate mutually exclusive 'cluster groupings' within which all nodes mapped close together will have been assigned to the same cluster. This situation occurs because it is not always possible to map and cluster together all nodes that are strongly related in a map bound by two-dimensional space. While most nodes will be both mapped and clustered together, there always remain a few nodes (identifiable as nodes of a different cluster colour) whose location cluster on the map diverge. These divergent nodes are often 'bridging nodes' between networks: they might be clustered in a number of groups (Waltman, 2016, pers. comm.). In the visualisations of archaeology, these bridging nodes help to identify underlying structures of difference (e.g. theoretical and methodological) that cross-cut many of the differences of period, place, and topic that appear to generate the identifiable clusters. Specific examples will be discussed in greater detail below.
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