Localize the third vector position using regexp

Hello everyone,

I am analyzing some data files in a loop, which look like this:

#------------------------------------------------------
# Atomistic spin configuration file for vampire v5+
#------------------------------------------------------
# Date: Thu Dec 21 02:16:27 2023
#------------------------------------------------------
Time: 1e-10
Field: -0	-0	-3
Temperature: 0
Magnetisation: 0.0276355	0.000325712	-0.999618
#------------------------------------------------------
Number of spin files: 1
spins-00000000.data

In particular, I am interested in the information localized after "Field:", which has the form of a three-dimensional vector (-0,-0,-3). I want to be able to have access to the third component of this vector, "-3". If I use:

field_str=regexp(meta_file_read,'(?<=^Field:\s+)\S+','match','lineanchors');

I am able to obtain the information localized in the first component of the field vector, "-0". Is there an efficient way to access the third component of the field vector using regexp?

Answer 1

[Stephen23]

txt = fileread('test.txt')

txt = 
    '#------------------------------------------------------
     # Atomistic spin configuration file for vampire v5+
     #------------------------------------------------------
     # Date: Thu Dec 21 02:16:27 2023
     #------------------------------------------------------
     Time: 1e-10
     Field: -0	-0	-3
     Temperature: 0
     Magnetisation: 0.0276355	0.000325712	-0.999618
     #------------------------------------------------------
     Number of spin files: 1
     spins-00000000.data'

rgx = '(?<=Field(\S+\s+){3})\S+';
out = regexp(txt,rgx,'once','match')

out = '-3'