Describe the bug
Bar Plots do not play nice with negative values:

• Unless panned/zoomed, the plot will only show y values >0 (Quadrant 1, assuming non-negative x-values)
  
• Error bars are drawn from the topmost point, which for negative values is 0
  

Negative values on bar plots are atypical, but I was looking at making waterfall charts:

You might recognize waterfall charts as a generalization of a Gantt chart:

I will probably work on this sometime soon-ish. I noticed it because I was thinking about implementing waterfall charts as bar charts with an extra std::shared_ptr<double> offsets parameter, but the handling of negative values put a damper on things.

To Reproduce
Create a bar plot with negative y values.

//xs, ys, yError
var barPlot = plt.PlotBar(new double[]{1,2,3}, new double[]{1,0,-1}, new double[]{1,1,1});

Screenshots
I embedded them in the list :/