For loop of an FFT script

Hello,

I have a script that works for a single file using dlmread, the output seems to work fine. I need to put it inside a loop but I am getting some errors.

Here is the scipt for a single file:

z = data(:,1);

y = data(:,2);

T=data(:,3);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% % fft method

[fhz,fft_spectrum] = do_fft(z(:),y(:));

[amplitude1, idx] = max(fft_spectrum);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

L = length(z);

fs = 1/mean(diff(z)); % Sampling Frequency

fn = fs/2; % Nyquist Frequency

yc = y - mean(y); % Sampling Interval

FTv = fft(yc)/L; % Fourier Transform

Fv = linspace(0, 1, fix(L/2)+1)*fn; % Frequency Vector

Iv = 1:length(Fv); % Index Vector

[max_FTv, maxidx] = max(FTv(Iv));

Fv_at_max_FTv = Fv(maxidx);

wavelength1=1/Fv_at_max_FTv;

Any help would be appreciated, thanks!

Answer 1

[CHIRANJIT DAS]

@Hussein Kokash Not sure whether your files are located in a single folder or not. If it is in single folder then you can make use of below code..

loc='/Volumes/Backup Plus/path/'; % put path of your data files
cd(loc)
fnames=dir(fullfile('*.txt')); % Put the extension of your files
output=[];

for i=1:numel(fnames)
    
    filename=fnames(i).name;
    data = dlmread(filename) % I would suggest you to use readmatrix instead of dlmread.
    z = data(:,1);
    y = data(:,2);
    T=data(:,3);
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % % fft method
    [fhz,fft_spectrum] = do_fft(z(:),y(:));
    [amplitude1, idx] = max(fft_spectrum);
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    L = length(z);
    fs = 1/mean(diff(z));                                 % Sampling Frequency
    fn = fs/2;                                              % Nyquist Frequency
    yc = y - mean(y);                                       % Sampling Interval 
    FTv = fft(yc)/L;                                        % Fourier Transform
    Fv = linspace(0, 1, fix(L/2)+1)*fn;                     % Frequency Vector
    Iv = 1:length(Fv);                                      % Index Vector
    [max_FTv, maxidx] = max(FTv(Iv));
    Fv_at_max_FTv = Fv(maxidx);
    wavelength1=1/Fv_at_max_FTv;
    
    output=[output;wavelength1];
    
end

If you want to save wavelength, then you can find it in output. You can save your desire outputs this way.