Provides a range of filters that can be applied to layers from the
    'ggplot2' package and its extensions, along with other graphic elements such
    as guides and theme elements. The filters are applied at render time and
    thus uses the exact pixel dimensions needed.

The function gggap() streamlines the creation of segments on
    the y-axis of 'ggplot2' plots which is otherwise not a trivial task to
    accomplish.

A variety of multivariable data summary statistics and 
    constructions have been proposed, either to generalize univariable analogs 
    or to exploit multivariable properties.
    Notable among these are the bivariate peelings surveyed by Green 
    (1981, ISBN:978-0-471-28039-2),
    the bag-and-bolster plots proposed by Rousseeuw &al (1999) 
    <doi:10.1080/00031305.1999.10474494>, and the minimum spanning trees used by
    Jolliffe (2002) <doi:10.1007/b98835> to represent high-dimensional 
    relationships among data in a low-dimensional plot.
    Additionally, biplots of singular value--decomposed tabular data, such as
    from principal components analysis, make use of vectors, calibrated axes,
    and other representations of variable elements to complement point markers
    for case elements; see Gabriel (1971) <doi:10.1093/biomet/58.3.453> and
    Gower & Harding (1988) <doi:10.1093/biomet/75.3.445> for original proposals.
    Because they treat the abscissa and ordinate as commensurate or the data
    elements themselves as point masses or unit vectors, these multivariable
    tools can be thought of as belonging to geometric data analysis; see Podani
    (2000, ISBN:90-5782-067-6) for techniques and applications and Le Roux &
    Rouanet (2005) <doi:10.1007/1-4020-2236-0> for foundations. 'gggda' extends
    Wickham's (2010) <doi:10.1198/jcgs.2009.07098> layered grammar of graphics
    with statistical transformation ("stat") and geometric construction ("geom")
    layers for many of these tools, as well as convenience coordinate systems
    to emphasize intrinsic geometry of the data.