problems with fitting curve from matrix data

I have problem in fitting curve. I want to specify the data of only one period and want to identify that this data is only in one period and extend this data. what can i do this?

Answer 1

[Dan Kenney]

I am doing the same thing now and I have been making new arrays of the intervals that I want to fit. I have not found a way to fit only certain intervals in sets of data.