PubMed Pairwise Co-Occurrence Matrix Construction and Visualization // Queries the 'NCBI' (National Center for Biotechnology Information) Entrez 'E-utilities' API to count pairwise co-occurrences between two sets of terms in 'PubMed' or 'PubMed Central'. It returns a matrix-like data frame of publication counts and can export hyperlink-enabled results in CSV or ODS format. The package also provides heatmap helpers for exploratory visualization of overlap patterns. Based on the method described in Becker et al. (2003) "PubMatrix: a tool for multiplex literature mining" doi:10.1186/1471-2105-4-61.