Features

facet_grid2() mirrors the axis options of facet_wrap2() but with a grid layout.
facet_manual() mimics the base R layout strategy for panels.
facet functions have a strip argument that allows greater control over the strips.
- strip_vanilla() allows control over clipping an sizes
- strip_themed(): allows more precise theme settings per strip
- strip_nested(): merges adjacent labels
guide_axis_manual() for greater control over axes.
stat_difference() for interpolated ribbons showing the difference between two lines.
help_secondary() for contstructing secondary axes

Adjustments

The free, axes and remove_labels arguments in facets now require less ambiguous input.
facet_nested()/facet_nested_wrap() now takes an element as nest_line argument.
facet_nested()/facet_nested_wrap() nesting is now controlled via the strip argument.
facet_wrap2() has the trim_blank option.
Position guides now have the colour argument to quickly set the colour for all theme elements.