ggdist: Visualizations of distributions and uncertainty

New features and enhancements:

• The stat_sample_... and stat_dist_... families of stats have been merged (#83).
  • All stat_dist_... stats are deprecated in favor of their stat_... counterparts, which now understand the dist, args, and arg1...arg9 aesthetics.
  • xdist and ydist can now be used in place of the dist aesthetic to specify the axis one is mapping a distribution onto (dist may be deprecated in the future).
  • Passing dist-like objects to the x or y aesthetics now raise a helpful error message suggesting you probably want to use xdist or ydist.
  • Restructured internals for stats and geoms makes it much easier to maintain shortcut geoms and stats, eliminating a large amount of code duplication (#106).
  • New expand parameter to stat_slabinterval() allows explicitly setting whether or not the slab is expanded to the limits of the scale (rather than implicitly setting this based on slab_type).
• The point_interval() family of functions can now be passed distributional and posterior::rvar() objects, meaning that means and modes (in addition to medians) and highest-density intervals (in addition to quantile intervals) can now be visualized for analytical distributions.
  • As part of this, multivariate distribution objects and rvars will generate a .index column when passed to point_interval() functions (#111). Based on a suggestion from @mitchelloharawild.
• New stat_ribbon() provided as a shortcut stat for stat_lineribbon() with no line (#48). Also, if you supply only an x or y aesthetic to geom_lineribbon(), you will get ribbons without a line (#127).
• One-sided intervals (i.e. quantiles) can now be calculated using ul() (upper limit) or ll() (lower limit), e.g. with point_interval() explicitly or via mean_ll(), median_ll(), mode_ll(), mean_ul(), median_ul(), or mode_ul() (#49).
• Constant distributions are now reliably detected in a variety of situations and rendered as point masses in both density plots and histograms (#103, #32).
• Minor improvements and changes to dotplot layouts that may result in minor changes to the appearance of existing dotplots:
  • Minor improvements to automatic bin width selection; the maximum dot stack height should be closer to or equal to scale more often.
  • A formerly-internal fudge factor of 1.07 for dot sizes is now exposed as the default value of the dotsize parameter instead of being applied internally. This fudge factor tends (in my opinion) to make dotplots look a bit better due to the visual distance between circles, but is (I think) better used as an explicit value than an implicit one, hence the change. This may create subtle changes to plots that use the dotsize or stackratio parameters, but allows those parameters to have a more precise geometric interpretation.

Documentation:

• New vignette for the stat_dotsinterval() sub-family: vignette("dotsinterval") (#120).
• Vastly improved and expanded documentation for the stat_slabinterval() and geom_slabinterval() family: each shortcut stat/geom now has its own documentation page that comprehensively lists all parameters, aesthetics, and computed variables, including those pulled in via ... from typically-paired geoms. These docs are auto-generated and should be easy to maintain going forward. (#36)
• The stat_lineribbon() and geom_lineribbon() family now also has separate documentation pages with a comprehensive listing of aesthetics and parameters (#107).
• Ridge plot-like example in vignette("slabinterval") using the new expand parameter (#115).

Deprecations and removals:

• The .prob argument, a long-deprecated alias for .width, was removed.
• The limits_function, limits_args, slab_function, slab_args, interval_function, and interval_args arguments to stat_slabinterval() were removed: these were largely internal-use parameters only needed by subclasses of the base class for creating shortcut stats, yet added a lot of noise to the documentation, so these were replaced with the $compute_limits(), $compute_slabs(), and $compute_intervals() methods on the new AbstractStatSlabinterval internal base class.

Bug fixes:

• Improved handling of NAs for analytical distributions.
• Fixed bug where within-bin order of dots in dotplots for "bin" and "weave" layouts could be incorrect with aesthetics mapped at a sub-bin level.
• stackratios that are not equal to 1 are now accounted for in find_dotplot_binwidth() (i.e. automatic dotplot bin width selection).
• Ensure distinct fill colors in lineribbons are still treated as distinct for grouping even if the fill_ramp aesthetic ramps them to the same color.