How to save 7 different large matrix (for Landsat 7 bands) in one variable?

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Meghraj Kc 2022-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/1816805-how-to-save-7-different-large-matrix-for-landsat-7-bands-in-one-variable

评论： Bjorn Gustavsson 2022-10-5

In this MATLAB code i want to save the surface reflectance for all the bands i.e., 7 bands in surface_Reflectance1 variable. The matrix size of one band is 7321*7351. So can you please suggest me how to save all the bands in one variable name.?

for dates1 =1:121
    for bands = 1:7
        if exist(fullfile(filepath1,date1(dates1).name,'L2C2'), 'dir')
            date_dir1 = dir(fullfile(filepath1,date1(dates1).name,'L2C2'));
            
            ImB1file1 = dir(fullfile(filepath1,date1(dates1).name,'L2C2','*B1.TIF'));
            Imfiles1_N = dir(fullfile(filepath1,date1(dates1).name,'L2C2',[ImB1file1.name(1:end-5),num2str(bands),'.TIF']));
            [A1, R] = geotiffread(fullfile(Imfiles1_N.folder,Imfiles1_N.name));
            
            
            Mtl2 = dir(fullfile(filepath1,date1(dates1).name,'L2C2','*MTL.txt'));
            [MTL_list1,value] = MTL_parser_L8(fullfile(Mtl2.folder,Mtl2.name));
            RMUL1 = 0.0000275;
            RADD1 = -0.2;
            
            Surface_Reflectance1(:,bands) = (RMUL1)*(single(A1))+(RADD1);
        end 
    end
end

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dpb 2022-10-4

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Makes no sense...you wrote "The matrix size of one band is 7321*7351." but in

Surface_Reflectance1(:,bands) = (RMUL1)*(single(A1))+(RADD1);

variable bands is 1, 2, ..., 7 subsequently so Surface_Reflectance1(:,bands) is and can only be a Nx7 array. Where are the other 7351-7 columns supposed to be coming from?

Meghraj Kc 2022-10-4

Sorry to misinterpret, you are correct i.e., bands are 1:7

I mean to say that the size of "A1" is 7321*7351 so, at the end when multiplying and adding with my scaling factor. I don't know how to save it for 7 bands.

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Answer 1

Bjorn Gustavsson 2022-10-4

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Break down your loops into something simpler first. Skip the outermost one and select one date that you know you have data from.

Also change your coding style, at least for the loop-variables. It is a mess to read date1(dates1) - that will be a source for unnecessary headakes. Change dates1 to i_date, or idx_dates just to make it clear what is the dates-array and what is the indices into that array. This will make a big difference in the long run.

% for i_dates =1:121
i_dates = 12; % if you have dat from that date 
for bands = 1:7
  if exist(fullfile(filepath1,date1(i_dates).name,'L2C2'), 'dir')
    date_dir1 = dir(fullfile(filepath1,date1(i_dates).name,'L2C2'));
    
    ImB1file1 = dir(fullfile(filepath1,date1(i_dates).name,'L2C2','*B1.TIF'));
    Imfiles1_N = dir(fullfile(filepath1,date1(i_dates).name,'L2C2',...
                              [ImB1file1.name(1:end-5),num2str(bands),'.TIF']));
    [A1, R] = geotiffread(fullfile(Imfiles1_N.folder,Imfiles1_N.name));
    
    Mtl2 = dir(fullfile(filepath1,date1(i_dates).name,'L2C2','*MTL.txt'));
    [MTL_list1,value] = MTL_parser_L8(fullfile(Mtl2.folder,Mtl2.name));
    RMUL1 = 0.0000275;
    RADD1 = -0.2;
    % Something like this will save a 7321 x 7351 image A1 into Surface_reflectance
    % for each band.
    Surface_Reflectance1(:,:,bands) = (RMUL1)*(single(A1))+(RADD1);
  end 
end

HTH

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Meghraj Kc 2022-10-4

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Now I am able to save per band. Also, I want to save per date also since, I have 161 total dates. It is not possible to run for individual date. How can I save per band?

clear all
if ispc
    filepath1 = ('Z:\ImageDrive\OLI.TIRS\L8\P039\R037');
elseif isunix
    filepath1 = ('/home/megh.kc/zdrive/ImageDrive/OLI.TIRS/L8/P039/R037');
end
date1 = dir(filepath1);
date1 ([1 2])= []; 
 for dates1 =1:161%size(date1,1)
    for bands = 1:7
        if exist(fullfile(filepath1,date1(dates1).name,'L2C2'), 'dir')
            date_dir1 = dir(fullfile(filepath1,date1(dates1).name,'L2C2'));
            
            ImB1file1 = dir(fullfile(filepath1,date1(dates1).name,'L2C2','*B1.TIF'));
            Imfiles1_N = dir(fullfile(filepath1,date1(dates1).name,'L2C2',[ImB1file1.name(1:end-5),num2str(bands),'.TIF']));
            [A1, R] = geotiffread(fullfile(Imfiles1_N.folder,Imfiles1_N.name));
            
            
            Mtl2 = dir(fullfile(filepath1,date1(dates1).name,'L2C2','*MTL.txt'));
            [MTL_list1,value] = MTL_parser_L8(fullfile(Mtl2.folder,Mtl2.name));
            RMUL1 = 0.0000275;
            RADD1 = -0.2;
            
            Surface_Reflectance1(:,:,bands) = (RMUL1)*(single(A1))+(RADD1); 

Bjorn Gustavsson 2022-10-5

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My suggestion is that you save data from separate dates into different directories. Something like this:

for iDate = 1:numel(Dates)
    currDirname = datestr(Dates(iDate,:),'yyyymmdd'); % or whatever format suits you
    mkdir(currDirname)
    % reading data
    % processing data
    savefile = sprintf('My-process.mat')
    savename = fullfile(currDirname,savefile)
    save(savename,'Surface_Reflectance1') % add other variables, or whatever
end

HTH

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