Text file for loop help

I have a text file (attached), which has 4 columns. I wanted to create separate text files out of this one text file based on the first column that is divided up into numbers (11,12,13,...) all the way until 290. I also wanted to pull out the first row of every text file and put it into one huge text file.

Below is an example of the code written, but I do not know how to integrate a for loop into this to perform those two actions.

clear all
fidi = fopen('1month290lags.txt','rt');
Glxc  = textscan(fidi, '%s', 'Delimiter','|');
frewind(fidi)
Glxcs = textscan(fidi, '%s', 'EndOfLine','\r\n');
fclose(fidi);
dlen = 4*fix(length(Glxc{:})/4);                          % Set Row Length
Glxcr = reshape(Glxc{:}(1:dlen), 4, [])';                  % Reshape & Transpose
LIdx=str2double(Glxcr(:,1))<=11
NewGlxc = Glxcs{:}(LIdx,:);                                 % Rows Of New Array
fido = fopen('1month290lags11.txt','wt')
fprintf(fido, '%s\n', NewGlxc{:});
fclose(fido)

Answer 1

[dpb]

Glxc  = textscan(fidi, '%s', 'Delimiter','|');

Why are you reading the numeric data as strings? Read it as numeric and the operations on finding the desired values then become trivial.

x=cell2mat(textscan(fidi, '', 'Delimiter','|'));
u=unique(x(:,1);             % find the unique values in the first column
for i=1:length(u)            % over all unique values
  dlmwrite('YourdesiredfilenameforUniqueCase(i)',x(x(:,1)==u(i),:))  % write data for each u
end

I don't understand the other request, sorry...