Color schemes

[tbreloff]

Support both discrete and continuous color schemes, probably through the color/markercolor/ribboncolor keywords.

When you pass a vector of vectors or vector of tuples into color, then the inner item will be treated as a color scheme. Color is determined by the z value if present, otherwise the y value?

See #4 (comment) and http://docs.ggplot2.org/current/scale_gradient2.html for examples of what to support.

I'd expect the first example to be generated something like:

using Plots, OnlineStats
y = cumsum(randn(100))
v = Variance()
sigma = Float64[(update!(v, yi); std(v)) for yi in y]
plot(y; c=:blue, ribbon = sigma, ribboncolor = (sigma, :blues))

[tbreloff]

I want to also make it easy to change pieces of the colors, but leave other pieces automated. For example, force alpha/opacity to a value, but still choose the RGB automatically. Likewise, you could fix green and blue and allow variations of red to be chosen. In order to accomplish this cleanly, I should probably have a ColorGenerator type. This could cover the cases I described, where the current color picking would be the default. It could also cover colors that are dependent on a z value, or some other color scale determined by data, such as those cases described above.

[tbreloff]

I'm working on color generation more (continued from JuliaGraphics/Colors.jl#18). I split off and added more color functionality, including a new algorithm for choosing colors automatically given a background color. The gist is that I pick an ordered subset of colors (which are sufficiently different from the background color) from a list of pre-generated "different colors". Automated colors for 15 lines on each background:

subplot(cumsum(randn(10,90),1), w=5, bg=[:white,:black,:grey,:orange,:blue,:red], n=6,nc=2)

[tbreloff]

I've made a lot of progress with the color scheme framework, adding gradients, different palette functions, etc. Plots like this are supported in Gadfly/Immerse (once I merge), although I really don't like the way the legends are implemented in Gadfly when trying to layer multiple series with a continuous color scale...

Here's some gradients I have right now: