How do a find a value of y for a known value of x?

I have a whole lot of data that has been collected in Matlab from an external device - an eye tracker. The device gives me a total time (x) of the data collection and a variety of things (y) that happened during that time. I need to pinpoint a certain time, T1, find out the number and durations of fixations (y) up to that point and do the same at another point, T2. The idea is to get a picture of what is happening between T1 and T2. I have tried inter1, but x and y are not the same length........ Any help will be appreciated - please keep it simple! Thanks!! :)

[Walter Roberson]

How do you know which x value goes with which y values ? Is y perhaps a cell array with as many entries as there are in x ?

[Patricia]

Thank you for replying. I actually don't know. The number of fixations varies all the time as does their duration. The crux of my research is about getting these values out of the mass of results that I have at particular point in time....... does this make sense? P