How to read only some lines and skip others

time,n0v_soma,n1v_soma,n2v_soma,n4v_dend,n5v_dend,n6v_dend,n7v_dend,n8v_dend,n9v_dend,n10v_dend,n11v_dend,n12v_dend,n13v_dend,n14v_dend,n15v_dend,n16v_dend,n17v_dend,n18v_dend,n19v_dend,n20v_dend,n21v_dend,n22v_dend,n23v_dend,n0Isyn,n1Isyn,n2Isyn,n0curr,n1curr,n2curr
0,-69.1127,-68.9,-65.2096,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-66.5,-2,-2,-2,0,0,0
0.027,-69.1062,-68.8937,-65.2083,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-66.4966,-2,-2,-2,0,0,0
0.054,-69.0996,-68.8874,-65.2069,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-66.4933,-2,-2,-2,0,0,0
0.081,-69.0931,-68.8811,-65.2056,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-66.4899,-2,-2,-2,0,0,0
0.108,-69.0865,-68.8747,-65.2043,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-66.4866,-2,-2,-2,0,0,0
0.135,-69.08,-68.8684,-65.2029,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-66.4833,-2,-2,-2,0,0,0
0.162,-69.0735,-68.8621,-65.2016,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-66.48,-2,-2,-2,0,0,0
0.189,-69.067,-68.8559,-65.2003,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-66.4766,-2,-2,-2,0,0,0
0.216,-69.0605,-68.8496,-65.1989,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-66.4733,-2,-2,-2,0,0,0
0.243,-69.054,-68.8433,-65.1976,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-66.47,-2,-2,-2,0,0,0

I want to read only the first 4 lines and first 4 columns skip the rest and also want to skip the header the output should be like this.

0,-69.1127,-68.9,-65.2096,
0.027,-69.1062,-68.8937,-65.2083
0.054,-69.0996,-68.8874,-65.2069
0.081,-69.0931,-68.8811,-65.2056

Answer 1

[per isakson]

>> cssm('cssm.txt')
ans =
         0  -69.1127  -68.9000  -65.2096
    0.0270  -69.1062  -68.8937  -65.2083
    0.0540  -69.0996  -68.8874  -65.2069
    0.0810  -69.0931  -68.8811  -65.2056

where

function  out = cssm( filespec )
    fid = fopen( filespec );
    cac = textscan( fid, '%f%f%f%f%*[^\n]', 4, 'Delimiter',',' ...
                ,   'CollectOutput',true, 'Headerlines',1 );
    [~] = fclose( fid );
    out = cac{:};
end

and cssm.txt contains your data

[Shivik Garg]

Thanks for your help

[Shivik Garg]

I just want to ask you if i want to extend it to more than 4 columns first 100 columns i want to select then how to do it

[per isakson]

Replace

'%f%f%f%f%*[^\n]'

by

[ repmat('%f',[1,100]), '%*[^\n]' ]

or if the file has exactly 100 columns by

repmat('%f',[1,100])

[Walter Roberson]

want_rows = 4;
want_cols = 100;
fmt = [repmat('%f', 1, want_cols), '%*[^\n]'];
cac = textscan( fid, fmt, want_rows, 'Delimiter',',' ...
              ,   'CollectOutput',true, 'Headerlines',1 );

[per isakson]

And combine all of it to

function  out = cssm( filespec, want_rows, want_cols )
    ....
end