ggplot2 0.8.3  (2008-XX-XX)
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New features

* alpha: new aesthetic, with scale alpha.  Where a geom has both fill and colour, alpha affects the fill.
* annotate: new annotate function to make it easier to add annotations to plots
* facet_grid now takes strip label function from parameter labeller, not theme setting
* facet_grid: gains as.table argument to control direction of horizontal facets
* fortify: full set of methods for turning data from the sp package into data frames that can be plotted with ggplot2
* geom_errorbarh: new geom for horizontal error bars
* labels_parsed and labels_bquote functions to make it easier to display expressions on facet labels
* scale_manual now supports breaks and limits 
* subset: experimental new feature.  Layers now have a subset argument, which takes subsets formatted like .(var1 < 5, var2 == 3) etc.
* xlim and ylim now work recognise Date and POSIXct classes to create date and date_time scales respectively

Dealing with missing values

* facet_wrap: add drop argument to control whether or not panels for non-existent combinations of facetting variables should be dropped or not.  Defaults to TRUE
* scale_discrete: empty factor levels will be preserved, unless drop = TRUE

Bug fixes

* added presidents dataset from book to package
* American spelling of color accepted in as geom parameter, and all colour scales have alias spelled color (e.g. scale_color_hue)
* facet_wrap: contents guaranteed to be clipped to panel
* facet_wrap: corrected labelling when facetting by multiple variables (thank to Charlotte Wickham for a clear test case)
* geom_histogram now works with negative weights (provided position = "identity").  This is useful for creating back to back histograms.
* geom_step: improve legend
* geom_text: better legend
* geom_vline, geom_hline, geom_abline: should work in yet more situations
* resolution: fixed bug in computation of resolution that lead to (e.g.) incorrect boxplot widths when there was only a single x value in a group.
* position_stack: fixed bug in detection of overlap for very large bins
* scale_discrete: factor levels no longer mistakenly reordered
* scale_hue: now spans full range of hue if it less than 360 degrees
* scale_hue: rotated default hue range by 15 degrees to avoid unfortunate red-green contrast in two colour case
* show now works with ggplot objects
* stat_sum: fixed bug which resulted in dropped aesthetics
* stat_summary: now warns when dropping records with missing values
* stat_summary: should be a little faster
* stat_summary: correctly passes ... arguments on fun.data
* theme_bw: corrected justification of axis.text.y
* trans: bug fixes to logistic transformation
* order aesthetic should work again