How can I crop a graph

How can i crop a graph using GUI and then do further mathematical actions on the cropped data?

if my graph has parts of irrelevant data in the beginning and end and i want to look at the graph and use only the relevant part

Answer 1

[Cris LaPierre]

The best method that comes to mind is to modify the data that is displayed (update line XData and YData) so just the relevant data is there. Once you have the X and Y data, you can do whatever you want mathematically. When you are done, you can update the line data again to see the new results.

Here's an example of what I mean.