MATLAB: Randomly Appearing Zeros in Data Output

accumarrayfor loopmatrixzeros

Hello!
I'm still working on some code I have asked about in previous questions. All seems to be going well except in my output I keep getting zeros unexpectedly and I can't seem to figure out why
The code opens data, uses accumarray to place the data into vectors and then writes the output of the vectors into a matrix. For some reason I seem to get random rows of zero in this matrix – and I cant seem to find out why
The code is below:
% Cycle through files rownum = 1;
for f = 1: numberOfFiles resFileName = fullfile(res_files,baseFileNames(f).name) Name = baseFileNames(f).name rawData = importdata(resFileName,' ');
   timeData = rawData.data(:,1);
   ampData = rawData.data(:,2);
   PIDget = Name(3:5)
   PID = str2num(PIDget)
   Task1.PID{f} = PID;
   binnum = 1 + floor(timeData(:) / 39);
   Task1.Amp(f).trial = accumarray( binnum, ampData(:), [], @(V) {V})
   Task1.Time(f).trial = accumarray( binnum, timeData(:), [], @(V) {V})
   numtrial = numel(Task1.Amp(f).trial)
%    for trialnum = 1:numel(Task1.Amp(f).trial)
binnum(end)
for trialnum = 1:binnum(end)
       for numbers = 1:numel(Task1.Amp(f).trial{trialnum})
     timedata = Task1.Time(f).trial{trialnum}(numbers);
ampdata = Task1.Amp(f).trial{trialnum}(numbers);
       DATA_raw(rownum,1) = PID;
       DATA_raw(rownum,2) = trialnum;
       DATA_raw(rownum,3) = timedata;
       DATA_raw(rownum,4) = ampdata;
       rownum = rownum + numbers;
       end
end
end
The output data file DATA_Raw looks like this…
2  3  114.080000000000  0.218000000000000
0  0  0  0
0  0  0  0
0  0  0  0
2  4  120.260000000000  0.0350000000000000
Where are these zero's coming from???
Thanks, ML

Best Answer

I am suspecting that it is coming from your rownum = ronum+numbers.
From your snippit rownum starts at 1 and then gets incremented by numbers. It's basically defining a row in DATA_raw and then defining another row at (rownum+numbers) further down for the next iteration. since numbers isn't 1 you won't get sequential rows of data. When that happens MATLAB will zero fill the empty spaces.
simple display of whats happening
    x=rand(1,4)
    x(5,:)=rand(1,4)
I see where this may have worked if you get PID, trailnum, etc as size numbers*1 matrix where you'd need to increment the indexing by numbers and not just 1. However you'll additionally need to DATA_raw(rownum:rownum+numbers-1,1) which will get a numbers*1 matrix to go into that space.
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