Surface plot using multiple excel files

I'm just a beginner with MATLAB so please bear with me :).

I need to represent my data using a 3D plot. I tried using the surf function but in my case this is a little bit tricky. From the code you will see that I am looping through multiple excel files to extract data from it. Using a 3-dimensional plot I need to represent my Fv array as the 'X' coordinate, my FTsiga as the 'Y' coordinate and the the third coordinate should be each excel file that I am looping through. A plot of (Fv,FTsiga) looks like the figure that is attached herewith.

The code that I have written so far couldn't seem to execute because MATLAB crashed due to insufficient memory or because it got stuck in a loop. The latter is more likely I guess.

% Matlab trial code: Trying to loop through excel files strored in directory

source_dir = 'C:\UTwente\Q4\Structural Health and Condition monitoring\Case Roadbridge (Zwartewaterbrug)\Excel data'
source_files = dir(fullfile(source_dir, '*xlsx'));
len = length(source_files);
matrix = zeros(len,32);

X = zeros(len,32); Y = zeros(len,32); Z = zeros(len,32);
%looping through excel file in directory
for i=1:len
  data= xlsread(source_files(i).name,'Measurement data');
  for j=1:32
      sig = data(:,j);
      sig = sig - mean(sig);                                      % Remove d-c Offset
      L = length(sig);
      Fs = 1000;                                                  % Sampling Frequency
      Fn = Fs/2;                                                  % Nyquist Frequency
      FTsig = fft(sig)/L;
      Fv = linspace(0, 1, fix(length(FTsig)/2)+1)*Fn;             % Frequency Vector
      Iv = 1:length(Fv);                                          % Index Vector
      FTsiga = double(abs(FTsig(Iv))*2);                          % Truncate, Magnitude, Convert To Double
      sgf_sm = sgolayfilt(FTsiga, 5, 501);                        % Create ‘sgolayfilt’ Filtered FFT
      [~, idx] = max( sgf_sm );                                   % Getting the value of the modal frequency
      peakfreq = Fv( idx );
      matrix(i,j) = peakfreq;                                     % Matrix of all peak frequencies
      [X,Y,Z] = meshgrid(Fv,FTsiga,i);
  end
  surf(Fv,FTsiga,i);
end

Answer 1

[Star Strider]

I just now read your email to me. (Normally, I do not reply to them.)

You probably do not need the loop. The fft function will operate on columns of the matrix to produce the Fourier transform for each column. The same applies to subtracting the mean of each column before you do the fft. You can then use surf (or ribbon or plot3) on the resulting matrix to plot it.

I would not do the sgolayfilt call in that loop. Wait until you get the rest of your code running before you apply it.

I cannot run your code, so this is the best I can do to reply.