Stacked bar chart

[erwald]

Hey,
I needed to write a GKStackedBarGraph class based on the regular GKBarGraph class, and figured it may be of general interest. It's basically the same as the bar chart, except each bar consists of several segments (stacks) of colour. I added an example so that you can take a look.

The protocol looks like so:

- (NSInteger)numberOfBars;
- (NSInteger)numberOfStacks;
- (NSNumber *)valueForBarAtIndex:(NSInteger)index stack:(NSInteger)stack;

@optional
- (UIColor *)colorForBarAtIndex:(NSInteger)index stack:(NSInteger)stack;
- (UIColor *)colorForBarBackgroundAtIndex:(NSInteger)index;
- (CFTimeInterval)animationDurationForBarAtIndex:(NSInteger)index;
- (NSString *)titleForBarAtIndex:(NSInteger)index;

Note: It's not very well tested. Also, its draw animation is not as pretty as it could be.
// E. G.