For loop not working through matrix

I am trying to pull the data from each row of the entire 100x2 int16 matrix of "cr" and print in my file 'conc.dat'. However, only one row is being printed, it does not seem like my for loop is going through the entire matrix. Can someone help me figure out why and how to fix this issue?

for k = 1:length(cr);
    row = cr(k,:);
    conc = counts(row(:,1));
    fileID = fopen('conc.dat','w');
    fprintf(fileID,'\n');
    fprintf(fileID,'%12.f\n',conc);
    fclose(fileID)
end

Answer 1

[DGM]

You're overwriting the file every single time you write a line. That's the difference between opening the file with 'w' permissions and 'a' (write-append) permissions.

There's no need to open and close the file every single time anyway. Just move that outside the loop.

cr = [1:10; 11:20].'
counts = 101:110;

fileID = fopen('conc.dat','w');
for k = 1:length(cr)
    row = cr(k,:);
    conc = counts(row(:,1));
    
    fprintf(fileID,'\n');
    fprintf(fileID,'%12.f\n',conc);
end
fclose(fileID);

[Grace Pooley]

Magic, thank you for the thorough explanation!