ggplot2 2.1.0

New features

• When mapping an aesthetic to a constant (e.g.
  geom_smooth(aes(colour = "loess")))), the default guide title is the name
  of the aesthetic (i.e. "colour"), not the value (i.e. "loess") (#1431).
• layer() now accepts a function as the data argument. The function will be
  applied to the data passed to the ggplot() function and must return a
  data.frame (#1527, @thomasp85). This is a more general version of the
  deprecated subset argument.
• theme_update() now uses the + operator instead of %+replace%, so that
  unspecified values will no longer be NULLed out. theme_replace()
  preserves the old behaviour if desired (@oneillkza, #1519).
• stat_bin() has been overhauled to use the same algorithm as ggvis, which
  has been considerably improved thanks to the advice of Randy Prium (@rpruim).
  This includes:
  • Better arguments and a better algorithm for determining the origin.
    You can now specify either boundary or the center of a bin.
    origin has been deprecated in favour of these arguments.
  • drop is deprecated in favour of pad, which adds extra 0-count bins
    at either end (needed for frequency polygons). geom_histogram() defaults
    to pad = FALSE which considerably improves the default limits for
    the histogram, especially when the bins are big (#1477).
  • The default algorithm does a (somewhat) better job at picking nice widths
    and origins across a wider range of input data.
  • bins = n now gives a histogram with n bins, not n + 1 (#1487).

Bug fixes

• All \donttest{} examples run.
• All geom_() and stat_() functions now have consistent argument order:
  data + mapping, then geom/stat/position, then ..., then specific arguments,
  then arguments common to all layers (#1305). This may break code if you were
  previously relying on partial name matching, but in the long-term should make
  ggplot2 easier to use. In particular, you can now set the n parameter
  in geom_density2d() without it partially matching na.rm (#1485).
• For geoms with both colour and fill, alpha once again only affects
  fill (Reverts #1371, #1523). This was causing problems for people.
• facet_wrap()/facet_grid() works with multiple empty panels of data
  (#1445).
• facet_wrap() correctly swaps nrow and ncol when facetting vertically
  (#1417).
• ggsave("x.svg") now uses svglite to produce the svg (#1432).
• geom_boxplot() now understands outlier.color (#1455).
• geom_path() knows that "solid" (not just 1) represents a solid line (#1534).
• geom_ribbon() preserves missing values so they correctly generate a
  gap in the ribbon (#1549).
• geom_tile() once again accepts width and height parameters (#1513).
  It uses draw_key_polygon() for better a legend, including a coloured
  outline (#1484).
• layer() now automatically adds a na.rm parameter if none is explicitly
  supplied.
• position_jitterdodge() now works on all possible dodge aesthetics,
  e.g. color, linetype etc. instead of only based on fill (@bleutner)
• position = "nudge" now works (although it doesn't do anything useful)
  (#1428).
• The default scale for columns of class "AsIs" is now "identity" (#1518).
• scale_*_discrete() has better defaults when used with purely continuous
  data (#1542).
• scale_size() warns when used with categorical data.
• scale_size(), scale_colour(), and scale_fill() gain date and date-time
  variants (#1526).
• stat_bin_hex() and stat_bin_summary() now use the same underlying
  algorithm so results are consistent (#1383). stat_bin_hex() now accepts
  a weight aesthetic. To be consistent with related stats, the output variable
  from stat_bin_hex() is now value instead of count.
• stat_density() gains a bw parameter which makes it easy to get consistent
  smoothing between facets (@jiho)
• stat-density-2d() no longer ignores the h parameter, and now accepts
  bins and binwidth parameters to control the number of contours
  (#1448, @has2k1).
• stat_ecdf() does a better job of adding padding to -Inf/Inf, and gains
  an argument pad to suppress the padding if not needed (#1467).
• stat_function() gains an xlim parameter (#1528). It once again works
  with discrete x values (#1509).
• stat_summary() preserves sorted x order which avoids artefacts when
  display results with geom_smooth() (#1520).
• All elements should now inherit correctly for all themes except theme_void().
  (@Katiedaisey, #1555)
• theme_void() was completely void of text but facets and legends still
  need labels. They are now visible (@jiho).
• You can once again set legend key and height width to unit arithmetic
  objects (like 2 * unit(1, "cm")) (#1437).
• Eliminate spurious warning if you have a layer with no data and no aesthetics
  (#1451).
• Removed a superfluous comma in theme-defaults.r code (@jschoeley)
• Fixed a compatibility issue with ggproto and R versions prior to 3.1.2.
  (#1444)