Computing turning angles from location data

So I have three nx4 arrays where n is one of 1500,2000 and 6000. The 2nd and 3rd columns are the x & y displacement values for a rat population ,the 4rd column is the time displacement and the 1th is the "tag number" which identifies the rat in question. I need to compute the mean of the cosines of the turning angles of my data. I need to compute this for each entire array, not just individual rats. I'm not even too sure of what the "turning angle" is, but i'm also a bit of a noobian to matlab so would really appreciate any help. This is an example of my data: 2342 0 0 0 2342 -1 2 13 4535 0 0 0 4535 -1 2 33 4535 -3 0 65 4535 -1 1 88 4535 -2 1 148 4535 -3 -1 188 4535 -1 1 201 4535 -1 1 214 4535 -1 0 241 4535 -3 -1 270 1492 0 0 0 1492 -1 0 57 1509 0 0 0 1509 -1 1 30

[Timothy Russell]

Sorry but I cant seem to make the data come out nicely! I tried to use the code button but it didnt work. Hopefully you can still make sense of it!