How to delete specific lines from a txt file?

Hello, this is my problem: Background: I am comparing 2 files that should match in the first column but one of the files skips some numbers, suppose (12,12), (13,13), (14,15)*, so until now I have use a code to find and display the mismatches on the screen and I manually delete the excess rows in the complete file and rerun the code until everything matchs. Problem: Now usually I have used this with small files not correcting more than 10 mismatches, the problem is that I have a big data set with over 1000 of mismatches, so I need a way to delete the complete row of the "leftovers" in the txt file. Next is shown my coding:

%r is the number of total rows
%the first part is made for fileA and fileB storing in E and G matrices
fid = fopen('fileA.txt');
num_ints = 23;
num_rows = r;
format = [repmat('%f ', 1, num_ints)];
G = textscan(fid, format, num_rows);
G = [G{1:num_ints}];
fclose(fid);

for a = 1:1:r
  if (E(a,1)~=G(a,1));
  disp(E(a,1));
  break
  end
end
disp ('End of search');

As always thank you for your help!

Answer 1

[Geoff Hayes]

Mario - which of your two matrices, E or G, do you wish to delete the excess row from? Your code compares the first column from each as

 if (E(a,1)~=G(a,1)); 
     disp(E(a,1)); 
     break 
 end

If you just wish to delete the row of E that fails the above condition, then why not try something like

 for a = 1:1:r 
    if (E(a,1)~=G(a,1)); 
        % remove row a from E
        E(a,:) = []; 
    end
 end

The above assumes that E is the matrix with excess rows that need to be deleted. For example

 E = [ 1 2; 2 3; 4 4; 3 5; 4 4; 6 7; 5 9];
 G = [ 1 3; 2 4; 3 8; 4 7; 5 2];

If we run the above code, then the third and sixth rows of E should be deleted.

Answer 2

[dpb]

Given your E and G arrays,

[~,idxE,idxG]=intersect(E(:,1),G(:,1));

write new files

   E(idxE,:) and G(idxG,:)

NB: Above assumes integers as shown in example so exact comparison will be reliable.

doc intersect % and friends for gory details...