How to make first derivative and second derivative of a 2D line

Recently, I have begun to use the igor to analysis the dates.
I meet a big problem to treat the date. Is there anyone please tell me how to make first derivative and second derivative of 2D line?
I think you'll have to clarify what you mean by a 2D line. Possibly, what you mean is referred to in Igor as "XY Data", and you simply need to use the Differentiate operation with the /X flag, once for the first derivative and again for the second derivative.

DisplayHelpTopic("Waveform Versus XY Data")
DisplayHelpTopic("Differentiate")
Thanks a lot for your reply. My date is the type of xy date Your suggestion is very useful for my date analysis.