MATLAB Code for the calculation of Velocity Autocorrelation Function (VACF) and Diffusion Coefficient (D) for SPC/E water molecules

I have a text file containing the data of coordinates of atoms (Hydrogens and oxygens) for different timesteps (0,10, 20, 30,......1000) with time interval of 10, where the 1st column is the name of the atoms (Oxygen, Hydrogen) and 2nd, 3rd and 4th columns have x, y, and z components. And the text file starts from the 1st line. So, for 36 atoms, first 36 rows of the text file is for 1st timestep (timestep=0), next 36 rows for timestep=10, and so on upto timestep 1000. How can I calculate the VACF and D using MATLAB code? It would be nice of you if you could help me in this case about coding portion.

[Walter Roberson]

https://www.ucl.ac.uk/~ucfbasc/Theory/vaf.html

[Md Ikram]

can you tell or elaborate how to proceed in the code?

[Walter Roberson]

https://github.com/tinevez/msdanalyzer appears to implement it.