Visualization of Data Envelopment Analysis Problems // High- dimensional visualization methods for data envelopment analysis (DEA), gathering in one place techniques that have appeared in the literature but remained scattered and largely unimplemented: cross-efficiency matrix unfolding, the Porembski network with lambda edges, principal component analysis biplots, multidimensional-scaling colour-plots, self-organizing maps, the Costa bi-dimensional efficient frontier, parallel coordinates, radar charts, panel-data trajectory biplots, peer and reference networks, and a set of descriptive plots. The package is built around a single validated dea_data() object and uses the 'Benchmarking' package as its DEA engine. The implemented methods draw on a body of literature; representative references include Doyle and Green (1994) doi:10.1057/jors.1994.84, Porembski, Breitenstein and Alpar (2005) doi:10.1007/s11123-005-1328-5 and Bana e Costa, Soares de Mello and Angulo Meza (2016) doi:10.1016/j.ejor.2016.05.012.