Store different size arrays in a matrix according to index in a loop

Hey,

Im using blim toolbox which creates lines (y*x matrix where x can have different sizes) stored in a 10x1 cell, every cell corresponding to one line. I have a dataset of more then 5000 files, each file with a 10x1 cell. I created a loop where it reads one cell for every file giving me the vector x and y of the correspondent line. I want to store the y values in a matrix where the y value is in the right x position, using the x vector as index for the position of y values. And filling the empty values with NaN.

My loop is:

for ifile = 1:size(imgfilenames,2) % process each file in the list

      imgfilename = imgfilenames{ifile};
      blimfilename = getentryname(blimdir, imgfilename, blimext); % get the blimline filename

      % load line 1 from blimline files
      [message blimlines blimsettings] = loadblimline(blimdir, blimfilename, line_1);

      if ~isempty(blimlines{line_1}) % if this blimline is not empty
          blimx = blimlines{line_1}(1,:); % horizontal coordinates (pixels!)
          blimy = blimlines{line_1}(2,:); % vertical coordinates (pixels!)
      end

end

I created a basic example where I'm trying to obtaining the following result in my matrix:

 47    61    62    52    66    64    51     5    29    53    12    15    68    15    74
 NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN    49     3    59    59    77    18
 21     6    58    32    66    41    36   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN

using:

a = [1:15; rand(1,15)];
b = [10:1:15; rand(1,6)];
c = [1:7; rand(1,7)];

abc = {a,b,c};

matrix = zeros(3,15);

for i = 1:3;

       x = abc{i}(1,:); % horizontal coordinates (pixels!)
       y = abc{i}(2,:); % vertical coordinates (pixels!)

end

I already tried padcat and padadd but it doesn't work inside my loop since the vectors are generated in every interaction of the loop.

Thanks in advance for helping me out!

[Guillaume]

Do you know the maximum x?

[Sara Antonio]

yes, it is the maximum number of pixels of the image on where the lines are created. In this case is 1601.

Answer 1

[Guillaume]

Since you know maximum x you can predeclare your final array:

maxx = 1601;
out = nan(1, maxx);

Then it's just a matter of simple indexing to fill that vector:

for ifile = 1:numel(imgfilename) % process each file in the list
    imgfilename = imgfilenames{ifile};
    blimfilename = getentryname(blimdir, imgfilename, blimext); % get the blimline filename
    % load line 1 from blimline files
    [message, blimlines, blimsettings] = loadblimline(blimdir, blimfilename, line_1);
    if ~isempty(blimlines{line_1}) % if this blimline is not empty
        blimx = blimlines{line_1}(1,:); % horizontal coordinates (pixels!)
        blimy = blimlines{line_1}(2,:); % vertical coordinates (pixels!)
        out(blimx) = blimy; 
    end
end

[Sara Antonio]

Thank you for helping me, but it didn't worked. The output was the last interection of the loop instead of saving all values. I changed the out matrix for the size of my final output:

time = length(imgfilenames); maxx = 1601; out = nan(time, maxx); (it is a 5551*1601 matrix)

What i'm trying to do is store every y array in each row in the right x position. Can't i specify inside the loop that I want to save every result like out(ifile) like i would do it if every result was the same size?

[Guillaume]

I recommend you use numel instead of length. It's safer as numel will work even if imgfilenames is a matrix.

out = nan(numel(imgfilename), maxx);
for ...
   ...
   if ...
      out(ifile, blimx) = blimy;
   end
end