How to delete lines in a text file?

I have thousands of datafiles with headerlines and then 2 columns of data. For example:

mmmmmm_0001.chi

datatype measurement

units

comment

   5.5993205E-01  0.0000000E+00
   5.7147706E-01  0.0000000E+00
   5.8302206E-01  0.0000000E+00
   5.9456706E-01  0.0000000E+00
   6.0611206E-01  5.9196600E+02
   6.1765701E-01  5.9167889E+02
   6.2920201E-01  5.9606128E+02
   6.4074701E-01  6.1506769E+02
   6.5229201E-01  6.2716541E+02
   6.6383702E-01  6.3965259E+02

To import them in another software without errors I need to modify all the files keeping the first 4 rows of headerlines, and deleting only the first 4 lines of data (with intensity = 0). There is a way to do this with MATLAB? I cannot read from line 5 and append the headerlines later because they are changing for each file (...001.chi, ...002.chi and so on). The task is quite easy: I only need to delete an interval of lines (from line x to line y) and save the file, but I could not find any answer on the previous topics.

Edit: see attached file

Answer 1

[Stephen23]

EDIT: now the the OP has actually posted a sample data file.

A very robust way to read is to use textscan, something like this:

% Read file data into MATLAB:
fid = fopen('measur_xknh2%20(1-x)kh_x1_1.txt','rt');
hdr = textscan(fid,'%s',4,'Delimiter','\n','Whitespace','');
dat = cell2mat(textscan(fid,'%f%f'));
fclose(fid);
% Remove rows with zeros in the last column:
dat = dat(dat(:,2)>0,:);
% Save data in a new file:
fid = fopen('newfile.txt','wt');
fprintf(fid,'%s\n',hdr{1}{:});
fprintf(fid,' %.7E  %.7E\n',dat.');
fclose(fid);

This code produces a copy of the original file, excluding the rows where the second column had value zero. To process a sequence of files you should read this:

http://www.mathworks.com/matlabcentral/answers/57446-faq-how-can-i-process-a-sequence-of-files