Implements a grammar of graphics on top of the 'base' graphics system. A 'bbplot' object is built incrementally with a '+' operator from data, aesthetic mappings and layers, then rendered with base graphics, so plotbb layers can be mixed with ordinary base plotting calls. The package provides layers for points, lines, bars, histograms, densities, boxplots, violins, ribbons, smooths, error bars and tiles, together with colour and other aesthetic scales, automatic legends, faceting, themes, coordinate flipping and significance annotations.