storing values in matrix

I have a script wherein I have two nested for loops. The first for loop goes into a series of five directories. The second for loop goes into files within the directories and performs a series of analyses on waveforms. I'm trying to store certain values each time the script makes a loop through one directory. There's something wrong with my syntax obviously because instead of creating a new column for each directory its just adding onto the column the new values for the subsequent directories. I'm having difficulties getting it to start a new column when it stores. Any help would be much appreciated! Here's an example of a value I'm wanting to store:

keep2=[]
for i=1:length(dirs)
for pp=1:length(files)
keep(:,pp)=(snr510(:,pp)>1)&(snr1015>1)&(snr1520)>1;
keep2=[keep2;keep(:,pp];
end
end

Again instead of storing the values each time I move through the loop into a new column it just adds onto keep2.

Answer 1

[Jan]

Do the directories have the same number of files? Then a 3D-array would be fine:

keep = zeros(1, length(dirs), length(files));  % Pre-allocate!
for i=1:length(dirs)
  for pp=1:length(files)
    keep(:, i, pp) = (snr510(:,pp)>1) & (snr1015>1) & (snr1520)>1;
  end
end

If the directories have a different number of files, you need a CELL:

keepC = cell(1, length(dirs));
for i=1:length(dirs)
  keep = zeros(size(snr510, 1), length(files));
  for pp=1:length(files)
    keep(:, pp) = (snr510(:,pp)>1) & (snr1015>1) & (snr1520)>1;
  end
  keepC{i} = keep;
end

[Katherine Anderson]

Thanks Jan! The cell seemed to work..although I missed the {i} when I first did it and had quite the time messing around with things. Now I have the values stored in the cells individually for each directory-I'm gonna go ahead and store that way from now on..although its created a few other complications in my script that I'll have to iron out..I appreciate the help!