Save output from for loop without overwriting previous outputs?

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Peter 2015-3-21

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https://ww2.mathworks.cn/matlabcentral/answers/184331-save-output-from-for-loop-without-overwriting-previous-outputs

评论： Geoff Hayes 2020-8-19

Let't say I want to save the output "Qv_maalt" of each iteration to a vector called "Final". Currently I have 10 files for the loop to process, and thus, 10 iterations.

Where do i put the for loop in order to avoid overwriting of the variable "Qv_maalt" at each iteration, and instead write the output of each iteration to the same vector, and thus ending up with a vector of 10 different values.

My current code reads:

close all
files = dir('*.mat');
for file = files'
  load([file.name]);
    dt = Data1_time_M_airsupply(end);
    hold on
    midling = ones(1, 1000)/1000;
    filtrering = filter(midling,1,Data1_M_airsupply_IIR_Filter);
    plot(filtrering)  
    deltaMass = filtrering(1) - filtrering(end);                      
    Qm = deltaMass / dt;                                           
    T = mean(Data1_T_orifice);                                      
    tempVektor = [35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25];
    densVektor = [1.145 1.164 1.183 1.204 1.225 1.246 1.269 1.292 1.316 1.341 1.367 1.394 1.422];
    Rho = interp1(tempVektor, densVektor, T);                       
    Qv_maalt = Qm / Rho;    
end

Apologies for lack of brevity.

Thanks in advance!

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采纳的回答

Geoff Hayes 2015-3-21

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Peter - just define the vector Final (you may want to come up with a more descriptive name for it) before entering the for loop and update it at each iteration. Something like

 files = dir('*.mat');
 Final = zeros(length(files),1);
 for k=1:length(files)
     load([files(k).name]);
     % etc.
     Qv_maalt = Qm / Rho; 
     Final(k) = Qv_maalt;
 end

The above assumes that Qv_maalt is a scalar. If it is a vector, then you will need to size Final accordingly. If Qv_maalt is of a different size on each iteration of the loop, then consider using a cell array for Final.

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Angus Horne 2019-4-24

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What do you do when you get the error 'Unable to perform assignment because the left and right sides have a different number of elements' after perfomring this command. I am trying to make all the locs values into an array as below however only seem to storing the final value - is this the source of my problem?

listing = dir('*.bmp');
%check listing is working by whos listing
firstimg = imread(listing(1).name);
Final = zeros(length(listing),1);
for n=1:length(listing)
    
    img = imread([listing(n).name]);
    G = img(:,:,2)-firstimg(:,:,2); % take green channel only
    G = 255*(G-min(G(:)))/(max(G(:))-min(G(:)));
    FG = abs(fftshift(fft2(G)));
    imagesc(log(FG));
    [X,Y] = meshgrid((1:size(FG,2))-ceil(size(FG,2)/2),(1:size(FG,1))-ceil(size(FG,1)/2));
    R = sqrt(X.^2+Y.^2);
    rprofile = [];
    for r = linspace(2,50,200)
        criteria = (R>r-2 & R<r+2);
        rv = double(FG(criteria)).*(2-abs(R(criteria)-r));
        rprofile = [rprofile,mean(rv(:))];
    end
    figure; plot(linspace(2,50,200),rprofile) 
    xlabel('Wavelength')
    ylabel('Intensity')
    pause(1);
    
    [pks,locs] = findpeaks(rprofile, linspace(2,50,200), 'MinPeakDistance', 47)
    pause (1);
    
    Final(n) = (locs);
   
end

Geoff Hayes 2020-8-19

AAA.mat

Turbulence Analysis answer moved here

Yes, I have tried that got a attached mat file, here as you can see I have got 13x4 matrix for 10 files, actually row 3 and 4 belongs to same input file B00003.. Is there any possibility to group this...