Tukey-style boxplots

[tlnagy]

@PeterJacko recently brought this to my attention. Currently, our boxplots look like this

Hadley Wickham has a great review (boxplots.pdf) and makes several suggestions on how to design boxplots. We violate a couple of these suggestions.

Improvements

1. Box plots should not be filled in
2. Median line should extend the full width
3. (optional) Add support for notched boxplots to show the confidence interval around the median

[wizofe]

Is this still under discussion? I think it's pretty important to have full width median lines in the plots.

[tlnagy]

I don't have the bandwidth to be developing Gadfly (maybe @bjarthur, or @Mattriks?) so I think it would be up to someone to take the time to submit a PR.

[technocrat]

@tlnagy , Gadfly is so polished, that I found it hard to believe that boxplot notches had not been implemented, and now I'm surprised again to find that it is the child of a small, loving family who actually have day jobs. So, I'm not complaining, and I'll peek under the hood to see if the thought that I could put together a PR worth anyone's time to look at is as totally delusional as I think it is.

The Tukey notch is the killer feature of boxplots, a side by side shows at a glance if the medians significantly differ by whether the notches overlap.

[bjarthur]

would be great to have a PR. Gadfly needs new developer blood.