Reference usage map

The reference usage map is a plot of the number of citations to each reference from cocitation analysis. The principal use of this type of map is to gain an idea of the dynamics of base knowledge in the specialty: 1) emerging new of groups of references representing new concepts in specialty, and 2) decline in use of groups of references representing obsolescence of concepts in the specialty.

Building the reference timeline.

• Before a reference timeline can be generated, you must first perform co-citation clustering.

• On the TFGUI select Cooccurrence > make crossmaps > reference usage. A separate windo will appear displaying the reference usage plot.

Description of the reference usage plot.

• The elements of the reference usage plot are shown in the figure below:

1. Plot area. The x position of each circle corresponds to a reference on the dendrogram, the y position of circle is the year. The size of the circle is proportional to the number of times that the reference was cited in the corresponding year.
2. Year axis. Years increase going up.
3. Cocitation clustering dendrogram. The dendrogram is identical to the RF to reference crossmap dendrogram.
4. Reference labels. Reference labels are identical to the RF to reference crossmap labels.
5. Crosshairs. Clicking the mouse in the plot area put a vertical and horizontal line on the plot that intersects at the point that was selected. This crosshair is useful for identifying the year and reference of selected circles on the map.
6. Annotate menu. The menu has functions to increase or decrease the circle sizes, zoom to interesting parts of the map, and to adjust plot margins.
7. Webpage menu. This menu has a control to generate a reference usage plot webpage that can be posted to a web server.