Stat.dodge

[Mattriks]

• I've updated the documentation to reflect these changes
• I've added an entry to NEWS.md
• I've added and/or updated the unit tests
• I've run the regression tests
• I've built the docs and confirmed these changes don't cause new errors

This PR:

• Adds Stat.dodge(position= , axis= ) which allows geometries, e.g. labels & errorbars, to be dodged/stacked
• Adds Geom.barerror(position= , axis= ) = Stat.dodge(position, axis) + Geom.errorbar
• has defaults Stat.dodge(position=:dodge, axis=:x)
• closes Geom.bar(position=:dodge) and Geom.errobar #525, closes Order of colors in dodged bar plot? #588, closes Misplaced label with multibar charts #733
• Also closes Text labels in bar plot with string x-coordinates. Compose.jl#206

Examples

Examples of dodged bar plots with errors and labels:

using Compose, DataFrames, RDatasets, Statistics
salaries = dataset("car","Salaries")
salaries.Salary /= 1000.0
salaries.Discipline = ["Discipline $(x)" for x in salaries.Discipline]
df = by(salaries, [:Rank,:Discipline], :Salary=>mean, :Salary=>std)
[df[i] = df.Salary_mean.+j*df.Salary_std for (i,j) in zip([:ymin, :ymax], [-1, 1.0])]
df[:label] = string.(round.(Int, df.Salary_mean))

p1 = plot(df, x=:Discipline, y=:Salary_mean, color=:Rank, 
    Scale.x_discrete(levels=["Discipline A", "Discipline B"]),
    ymin=:ymin, ymax=:ymax, Geom.errorbar, Stat.dodge,
    Geom.bar(position=:dodge), 
    Scale.color_discrete(levels=["Prof", "AssocProf", "AsstProf"]),
    Guide.colorkey(title="", pos=[0.76w, -0.38h]),
    Theme(bar_spacing=0mm, stroke_color=c->"black")
)
p2 = plot(df, y=:Discipline, x=:Salary_mean, color=:Rank, 
    Coord.cartesian(yflip=true), Scale.y_discrete,
    label=:label, Geom.label(position=:right), Stat.dodge(axis=:y),
    Geom.bar(position=:dodge, orientation=:horizontal), 
    Scale.color_discrete(levels=["Prof", "AssocProf", "AsstProf"]),
    Guide.yticks(orientation=:vertical), Guide.ylabel(nothing)
)
hstack(p1,p2)

Here's an example of a stacked bar plot with labels:

p3 = plot(df, x=:Discipline, y=:Salary_mean, color=:Rank, 
    Scale.x_discrete(levels=["Discipline A", "Discipline B"]),
    label=:label, Geom.label(position=:centered), Stat.dodge(position=:stack),
    Geom.bar(position=:stack)
)

[codecov-io]

Codecov Report

Merging #1240 into master will increase coverage by 0.11%.
The diff coverage is 89.18%.

@@            Coverage Diff             @@
##           master    #1240      +/-   ##
==========================================
+ Coverage   85.67%   85.79%   +0.11%     
==========================================
  Files          35       35              
  Lines        4085     4112      +27     
==========================================
+ Hits         3500     3528      +28     
+ Misses        585      584       -1

Impacted Files	Coverage Δ
src/geom/bar.jl	91.85% <100%> (ø)	⬆️
src/geom/errorbar.jl	91.89% <83.33%> (-5.34%)	⬇️
src/statistics.jl	90.64% <91.66%> (+0.02%)	⬆️
src/scale.jl	94.51% <0%> (+0.04%)	⬆️
src/guide.jl	84.87% <0%> (+1.21%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update aa8dff9...1a355f6. Read the comment docs.

[bjarthur]

this looks great as usual. is there a better name for barerror though? the difference with errorbar might not be obvious to a newcomer.

[Mattriks]

I think Geom.barerror is easy to remember. I've also tweaked Stat.dodge so that Geom.barerror and Geom.errorbar behave in the same way for simple bar plots (without stacking/dodging):

df2 = by(dataset("car","Salaries"), [:Rank], :Salary=>mean, :Salary=>std)
[df2[i] = df2.Salary_mean.+j*df2.Salary_std for (i,j) in zip([:ymin, :ymax], [-1, 1.0])]

p1 = plot(df2, x=:Rank, y=:Salary_mean, color=:Rank,
    Scale.x_discrete, Guide.xlabel(nothing),
    ymin=:ymin, ymax=:ymax, Geom.errorbar, Geom.bar,
     Guide.colorkey(title="", pos=[0.05w,-0.4h])
)
p2 = plot(df2, x=:Rank, y=:Salary_mean, color=:Rank,
    Scale.x_discrete, Guide.xlabel(nothing),
    ymin=:ymin, ymax=:ymax, Geom.barerror, Geom.bar,
     Guide.colorkey(title="", pos=[0.05w,-0.4h])
)
hstack(p1, p2)

Note that Geom.barerror will also work with points, lines, etc.

[Mattriks]

This PR is ready to be merged, if there are no other suggestions.

[bjarthur]

@tlnagy can you please comment?

Stat.dodge is fantastic, and it's great to close these old issues.

i still really don't like Geom.barerror though. just too confusing with Geom.errorbar. and it's only a convience function for Stat.dodge + Geom.errorbar.

i'd suggest just removing Stat.barerror. the rest of this PR is ready to merge. can always add it later if we decide the convenience is nice. but difficult to remove later since we're at 1.0, and removing it would be a breaking change.

[tlnagy]

I strongly agree with @bjarthur here that Stat.barerror will lead to confusion and I personally don't see the need for it.

Stat.dodge is fantastic, and it's great to close these old issues.

Agreed. This is a great contribution @Mattriks!

[Mattriks]

Ok, I removed Geom.barerror, added some minor fixes, updated documentation, and rebased - done!

[bjarthur]

thanks!