Hi pauli,
I don't understand the problem.
Is it reading the file or sorting the data?
To read in the file try something like this:
--
clear all; clc;
file='abaqus.txt';
fid=fopen(file);
data=textscan(fid,'%f %f %f %f','HeaderLines',3,'Delimiter',' ','MultipleDelimsAsOne',1);
fclose(fid);
data...