Reading txt file by character number defined columns

Hi guys, I am trying to read in data from a GRO file where the data is organized into columns that are defined by character numbers. For example, on any given row, characters 1-5 will have one type of data, 6-8 will have a different piece of data, and so on.

What's the best function to use read this file into an array?

Thanks! Nikolay

Answer 1

[per isakson]

The gro file format is described at Gromacs. There is no best way to read gro-files with Matlab - I think. One way is:

    fid = fopen( 'cssm.txt' );
    rw1 = fgetl( fid );
    rw2 = fgetl( fid );
    N   = str2double( rw2 );
    ca1 = textscan ...
        ( fid, '%5d%-5s%5s%5d%8.3f%8.3f%8.3f%8.4f%8.4f%8.4f', N, 'Delimiter', '' );
    ca2 = textscan( fid, '%f%f%f' );
    fclose( fid );

where cssm.txt contains

    MD of 2 waters, t= 0.0
        6
        1WATER  OW1    1   0.126   1.624   1.679  0.1227 -0.0580  0.0434
        1WATER  HW2    2   0.190   1.661   1.747  0.8085  0.3191 -0.7791
        1WATER  HW3    3   0.177   1.568   1.613 -0.9045 -2.6469  1.3180
        2WATER  OW1    4   1.275   0.053   0.622  0.2519  0.3140 -0.1734
        2WATER  HW2    5   1.337   0.002   0.680 -1.0641 -1.1349  0.0257
        2WATER  HW3    6   1.326   0.120   0.568  1.9427 -0.8216 -0.0244
       1.82060   1.82060   1.82060