addPolygon enhancements

[ethanbsmith]

1. support log y axis
2. support border color
3. support "sidelsss" borders. i.e. only top and bottom borders

[ethanbsmith]

example of "sideless" border that not only gives a clean look, but doesnt have sides that interfere with the candles

[joshuaulrich]

Thanks for working on this! Can you provide some code to reproduce your example plot before and after the changes?

[ethanbsmith]

i cant produce that exact plot as it uses quantmod candle plotting and that doesnt work with log yet (this fix a prerequisite)
i did t test this pr doesnt break quantmod::add_BBands()
i also used this to test correctness:

plot(Cl(as.xts(sample_matrix)), log = TRUE)
addPolygon(as.xts(sample_matrix)[,2:3], col = adjustcolor("orange", alpha.f = .25), border = "orange", on = 1)

[joshuaulrich]

I'm not sure why you mention quantmod::add_BBands()... quantmod doesn't use plot.xts(). It hasn't been back-ported.

[ethanbsmith]

i thought the chart_series and its ilk were based on plot.xts and wanted to make sure i didnt break that. my bad. just ignore that part

[joshuaulrich]

It's the other way around. plot.xts() was basically chart_Series() code... until I did that massive refactor to support a log y-axis.