How to group data in cells?

Hello,

My code works on a data file. By loading the file, I have a 5xn matrix (n is approximately BIG). Each column represents a point and are calculated by time, from 0 to 4500 several times. Time lapses between points are not equal. So my data looks like:

t1 t2 ... tn

y1 y2 ... yn

x1 x2 ... xn

So coordinates x and y haven't any kind of logic order.

Other rows are x' y' and energy, but are not needed for what I want now. I'm trying to group all points into a 2D meshgrid and calculate it's fractional ammount in order to plot a pcolor.

How could I do it? I sincerely have no idea where to start from.

Thanks for your answers.