Geom.rect

[Mattriks]

Two instances of RectangularBinGeometry are necessary:

• Geom.rectbin which calls Stat.rectbin (takes x & y aesthetics)
• Geom.rect which calls Stat.Identity (takes xmin, ymin, xmax, ymax)

The former currently exists, this PR adds the latter, and fixes issues #771 & #845.
Note the name Geom.rect is used rather than Geom.rectangle to avoid conflicts with Compose.rectangle (which is widely used without the package specifier in Gadfly code).

Here is an example:

theme1 = Theme(default_color=RGBA(0, 0.75, 1.0, 0.5))
D = DataFrame(x=[0.5,1], y=[0.5,1], x1=[0,0.5], y1=[0,0.5], x2=[1,1.5], y2=[1,1.5])
pa = plot(D, x=:x, y=:y, Geom.rectbin, theme1)
pb = plot(D, xmin=:x1, ymin=:y1, xmax=:x2, ymax=:y2, Geom.rect, theme1)
hstack(pa, pb)

[codecov-io]

Codecov Report

Merging #993 into master will increase coverage by 0.12%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #993      +/-   ##
==========================================
+ Coverage   78.99%   79.12%   +0.12%     
==========================================
  Files          33       33              
  Lines        4057     4058       +1     
==========================================
+ Hits         3205     3211       +6     
+ Misses        852      847       -5

Impacted Files	Coverage Δ
src/geom/rectbin.jl	80.55% <100%> (+9.12%)	⬆️
src/Gadfly.jl	74.02% <0%> (+0.25%)	⬆️
src/coord.jl	84.46% <0%> (+0.97%)	⬆️

---

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 13eba8b...bd0a78d. Read the comment docs.

[bjarthur]

ggplot uses geom_rect and geom_tile. should we follow suit?

http://ggplot2.tidyverse.org/reference/geom_tile.html

[Mattriks]

I prefer Geom.rectbin (rather than Geom.tile), and I don't think we should always follow suit.

[bjarthur]

i find Geom.rectbin confusing given that it doesn't actually bin the data, like Geom.hexbin does.

[Mattriks]

My suggestion is to open a new issue about the naming of Geom.rectbin if you want to change it.