How to export data from matlab to csv file from loop?

I have a bunch of data from a for loop that I need to export from matlab to csv file. I tried csvwrite('test.xlsx',data). When I open up the csv file, the data for a single iteration comes up. How can I get the data from every iteration to export to the csv file?

if true
  % code
end
fileFolder = fullfile(matlabroot, 'toolbox', 'images', 'imdata');
dirOutput = dir('/Users/JessFlores/Documents/MATLAB/XrayEye_*.tiff');
fileNames = {dirOutput.name}'
numFrames = numel(fileNames)
figure(); hold on
  for p = 0001:numFrames
      sequence(:,:,p) = imread(fileNames{p});
      %intensity plot info
      [x,y] = size(sequence(:,:,p));
      X = 1:x;
      Y = 1:y;
      [xx,yy] = meshgrid(Y,X);
      i = im2double(sequence(:,:,p));

        %maz and FWHM x and y from plot
        [mz,k] = max(i(:));
        [ix,jy] = ind2sub(size(i),k);
        [ix,jy,mz];

        %max intensity coordinates in microns
        %pixel size is 6.45x6.45 microns
        ix = 6.45*ix;
        jy = 6.45*jy;
        [ix,jy,mz];
        mhz = 0.5*mz;
        [ihx,jhy]=ind2sub(size(i),k);
        [ihx,jhy,mhz];
        FWHMx = abs(ix-ihx)*2;
        FWHMy = abs(jy-jhy)*2;

        %table of data from plot
        f = figure;
        data = [ix,jy,mz,FWHMx,FWHMy];
        colnames = {'X(Zmax) [um]', 'Y(Zmax) [um]', ...
            'Zmax/Max Intensity', 'FWHMx [um]', 'FWHMy [um]'};
        t = uitable(f, 'Data', data, 'ColumnName', colnames, 'ColumnWidth', {120});
        t.Position(3) = t.Extent(3);
        t.Position(4) = t.Extent(4);

        %make subplot of table and intensity plot
        subplot(2,1,1) = mesh(xx,yy,i); colorbar;
        title('Intensity of Beam Image as a Function of Pixel Position');
        xlabel('X(pixels)');
        ylabel('Y (pixels)');
        zlabel('Intensity (double precision corrected) [a.u.]');

      csvwrite('test.csv', data); 
    end

hold off

Answer 1

[Walter Roberson]

Use dlmwrite() with the -append flag. http://www.mathworks.com/help/matlab/ref/dlmwrite.html