
pie charts, pareto charts
label values at points and bars?

On the fly generation of PNG or JPEG images

Errors detected:
1. Playing with the background color and x or y grid
lines I realized that the setting of 'grid_lines'
color does not functions. 
2. I can change separately x grid lines or y grid
lines yet. The problem is that when you change either
color then the background color disappiers (becomes
white).
3. The title of the graph appeared with the bottom of
the letters erased. I was tying to fix with
graph_border setting but did not work.
4. It seems that the "" in the title does not work but the sub_title option
is working (also the documentation is saying that is deprecated).



Long term:
control charts
3-D charts?
x-ticks numerical, not just labels
	- spaces the data points out correctly along x-axis?
