Loading data to vector rather than cell in MATlab - matlab

Question

I load data from text files into my MATlab function using this code:
data = cell(h.numDirs, numDataFilesInFirstDir);
for d = 1:h.numDirs
% Code to set fileNames, iDir
for t = 1:size(fileNames,1)
fId = fopen([iDir, '/', fileNames{t}]);
% Drop the first two lines (column headers)
for skip = 1:2
fgets(fId);
end
U_temp = fscanf(fId, '%f %f', [2, Inf]);
U_temp = U_temp'; % ' transpose (syntax highlighting on SO)
data(d, t) = {U_temp(:,2)};
fclose(fId);
end
end
The files should each have the same length (at least for varying t, usually for varying d or else I have problems later)
Should I be (/ How can I) simplify the code here to avoid (unnecessary?) cells?
I could scan the first data set, then use something like
data = zeros(h.numDirs, numDataFilesInFirstDir, lengthOfFirstFile)
but I don't know if that would be any better. Is that a 'better' solution/method?

Answer 1

I would use dlmread instead of fscanf. Data type is hard since your dimensions vary. I wouldn't pad arrays... any benefit from not using cells would be overcome by the extra complexity and memory hit. Cell arrays are a reasonable choice. I wouldn't worry about preallocation too much in this case actually. Below is a similar option using structs with dynamic field names that embed the source directory and filename, for later reference.
data = struct();
for d = 1: ...
for t = 1: ...
file = fullfile(iDir, fileNames{t});
range = [3, 1, inf, 2];
dlm = ' ';
Utemp = dlmread(file, dlm, range);
data.(iDir).(fileNames{t}) = Utemp(:, 2);