Segment Geometry

[Mattriks]

A geometry for line segments/vectors/arrows. There is an example in the file geom_segment.md. This feature was previously requested in Issues #608 and #791. My current code will work for regular plots, but not yet for subplot_grid. I'll attempt to implement that sometime soon!

[tlnagy]

Hey @Mattriks, if you have time, can you rebase this on the latest master? Lets check if it works with all the recent changes and make sure it's all okay on 0.5. I think this would be a cool geometry to have.

[coveralls]

Coverage decreased (-0.4%) to 65.072% when pulling 05d8ef1 on Mattriks:Geom_segment into 4a36837 on dcjones:master.

[coveralls]

Coverage decreased (-0.4%) to 65.072% when pulling 05d8ef1 on Mattriks:Geom_segment into 4a36837 on dcjones:master.

[coveralls]

Coverage decreased (-0.4%) to 65.072% when pulling ef675b3 on Mattriks:Geom_segment into 4a36837 on dcjones:master.

[coveralls]

Coverage decreased (-0.4%) to 65.072% when pulling ef675b3 on Mattriks:Geom_segment into 4a36837 on dcjones:master.

[coveralls]

Coverage decreased (-0.4%) to 65.072% when pulling ef675b3 on Mattriks:Geom_segment into 4a36837 on dcjones:master.

[Mattriks]

I've tested this now on Julia 0.5-rc2. The example in the file geom_segment.md works. Also, this Segment Geometry works when using with Geom.subplot_grid.

[lobingera]

i wanted to report an issue on this issue, but it was just a githup hiccup...

[tlnagy]

@Mattriks Awesome. Could you add some tests?

[tlnagy]

I got to play around with this and looks good!

The only thing is that the arrowheads when calling Geom.vector look a little funky:

plot(x=rand(1:10, 10), y=rand(1:10, 10), xend=rand(1:10, 10), yend=rand(1:10, 10), Geom.vector)

And they don't behave properly when one of the axes is logged

[tlnagy]

Actually, the first one is caused by not having a square axis ratio. But in general, I would think that you don't want scaling and transformations to apply to the arrowheads.

[Mattriks]

I've implemented a new and improved Geom.vector (I've also included tests). In Gadfly, the current situation is that no information about Scales is passed to the geometry render functions. But for rendering vectors properly, info about the x and y scales must be provided. That is, the user must manually provide a Scale object (with a minvalue and maxvalue) for both axes. I will look into automating this in the future. Here is a current working example:

srand(1234)
D = convert(DataFrame, 99*rand(4, 4)+0.5)
xsc  = Scale.x_continuous(minvalue=0.0, maxvalue=100)
xlogsc  = Scale.x_log10(minvalue=1, maxvalue=100)
ysc  = Scale.y_continuous(minvalue=0, maxvalue=100)
xsqrtsc  = Scale.x_sqrt(minvalue=0, maxvalue=100)
layer1 = layer(x=:x1, y=:x2, xend=:x3, yend=:x4, Geom.vector)

pa = plot(D, layer1, xsc, ysc,
Guide.title("Plain scales"), Guide.ylabel(nothing), Guide.xlabel(" "))
pb = plot(D, layer1, xlogsc, ysc,
Guide.title("Semi-log"), Guide.ylabel(nothing), Guide.xlabel("x"))
pc = plot(D, layer1, xsqrtsc, ysc,
Guide.title("√x"), Guide.ylabel(nothing), Guide.xlabel(" "))

[coveralls]

Coverage increased (+0.3%) to 65.863% when pulling 1670e74 on Mattriks:Geom_segment into f6183ac on dcjones:master.

[tlnagy]

Very nice! What do you think about filled-in arrowheads? Whenever I think of vector fields, I always think of something like this:

(https://en.wikipedia.org/wiki/Vector_field)

[Mattriks]

Some extra attributes (example below). Wrt gradient vectorfields, that could be implemented as function Geom.gradvectorfield(z, x, y) (returning a SegmentGeometry), just as Geom.contour(z,x,y) returns a LineGeometry. That's a feature for the future, need to get Geom.segment merged first.

srand(123)
D = convert(DataFrame, 99*rand(4, 4)+0.5)
D[:col] = ["a","b","c","d"]

xsc  = Scale.x_continuous(minvalue=0.0, maxvalue=100)
ysc  = Scale.y_continuous(minvalue=0.0, maxvalue=100)
theme1 = Theme(line_width=3pt, line_style=[4mm,1mm], key_position=:none)
lf(x) = layer(x=:x1, y=:x2, xend=:x3, yend=:x4, x, color=:col)

pa = plot(D, lf(Geom.vector), xsc, ysc, Theme(key_position=:none))
pb = plot(D, lf(Geom.vector(filled=true)), xsc, ysc, theme1)

[coveralls]

Coverage increased (+0.3%) to 65.864% when pulling 9adbbf9 on Mattriks:Geom_segment into 30670b3 on dcjones:master.

[tlnagy]

That looks awesome. Personally, I like filled arrows to be the default, but that can changed in the future.

I've looked through this and I think it all looks good. LGTM. @shashi what do you think?

[tlnagy]

Is the top-level if statement necessary because render doesn't get scale information right now? Because this looks a bit hacky.

[Mattriks]

Scales are needed to stop arrowheads looking strange. Segments without arrowheads are not affected i.e. Geom.segment(arrow=false)

[tlnagy]

I see. I guess eventually we'll want to get rid of that when we pass Scales to render.

[tlnagy]

Alright. LGTM.