Pie chart with NaN in dataset does not trigger touchEvent

What steps will reproduce the problem?
1. Open CPTestApp-iPad
2. In CPTestApp_iPadViewController.h, add in <CPPiechartDelegate>
3. In CPTestApp_iPadViewController.m, implement 
-(void)pieChart:sliceWasSelectedAtRecordIndex
4. Add a breakpoint/print statement to the function in step 3
5. Make note the dataset is [20.0, 30.0, NaN, 60.0]
6. Build and run the application (simulator)
7. Touch red slice (index 0)
8. Touch event should trigger
9. Touch green slice (index 1)
10. Touch event should trigger
11. Touch yellow slice (index 3)

What is the expected output?
12. Touch event should trigger

What do you see instead?
12. Touch event does not trigger

What version of the product are you using? On what operating system?
Core-plot 0.2.2, Mac OSX 10.6.5, Xcode IDE, on Simulator

Please provide any additional information below.
I believe the NaN data offsets the index, which causes the function that 
invokes the delegate touch event to not find a proper index.

Original issue reported on code.google.com by pkjai1...@gmail.com on 25 Nov 2010 at 8:12

piaoyongren / core-plot

Pie chart with NaN in dataset does not trigger touchEvent #227