Understanding Core Data - Research Fronts
What are research fronts? A research front is a group of highly cited
papers, referred to as "core papers," in a specialized topic defined by
a cluster analysis. Research fronts offer an alternative classification
scheme for highly cited papers since the assignment of papers to a
research front is not based on the journal categories used in
Essential Science Indicators.
A measure of association between highly cited papers is used to form
the clusters. (See the
Cited Papers section for an explanation of the selection
criteria.) That measure is the number of times pairs of papers have
been co-cited, that is, the number of later papers that have cited both
of them. Clusters are formed by selecting all papers that can be linked
together by a specified co-citation threshold.
The clusters are named using a semi-automatic process based on
frequently occurring words and phrases. Statistical characteristics of
each cluster are also determined, including the number of highly cited
papers, the sum of their citation frequencies, the citations per paper,
and the mean year of papers in the front. The number of highly cited
papers gives an indication of the size of the foundation literature;
the sum of citation frequencies reflects the size of the research
front; the citations per paper the degree of concentration, and the
mean year of papers the currency, or "hotness," of the cluster.
Research fronts are assigned to the
broad fields based on the field of the most frequently
occurring journal in the front.
Only those fronts meeting a minimum size threshold and high average
currency are included in Essential Science Indicators.
Currency is determined by calculating the mean of the years of
publications of the highly cited papers.