sorting data using logic

Hello,

In my simulations two particles (named 13 and -13) are generated and hit these four planes and the information of position (x,y,z) and direction (Vx,Vy,Vz), energy and the event number (I have 500,000 events) are recorded for each as dmp.txt. I am going to sort these data in a way I can have one row for each event as shown in the figure that means if the first column and the last column of each row are same, the rows must br merged into one row . As the data is big, using loops will make it very slow and difficult. Could you please suggest me other methods that I can try? Please find a sample of data file and the procedure attached.

Thank you in advance.

[Stephen23]

Duplicate:

https://www.mathworks.com/matlabcentral/answers/1720910-merge-rows-based-on-conditions-in-the-coulmns