Core plot ios user interaction

Question

I am using core plot to display a line graph in my iphone app but I want to allow user interaction in this graph. By user interaction I mean when a user touches a spot on the graph it should display the corresponding x and y values. This is similar to the what I am looking for -

Can some one please link me to some tutorial on how to do this or show some code on how to do it. Thanks

Answer 1

You can use a second scatter plot and an annotation to display the selection line and label. The "Selection Demo" in the Mac version of the CPTTestApp example app shows one way to do this. The demo limits the selection to data points on the plot. If you want to respond to touches anywhere in the plot area, implement the -plotSpace:shouldHandlePointingDeviceXXXXEvent:atPoint: plot space delegate methods to control the selection line. Use the plot space to convert the given point to your data coordinates.